By Pulp & Paper Canada
By Pulp & Paper Canada
BEFORE FOCUSING on the outlandish and practical possibilities that nanotechnology can bring to society, and more specifically papermaking and paper itself, first consider the promise of nano from the…
BEFORE FOCUSING on the outlandish and practical possibilities that nanotechnology can bring to society, and more specifically papermaking and paper itself, first consider the promise of nano from the context of history.
Whenever humankind has reached for the impossible, for something outside and beyond our most profound knowledge, there has always been a common characteristic for discovery. Drive, focus, determination, intellect and, even greed, were all-important, but desire was arguably the most essential element of success.
European explorers (and their royal sponsors) had the desire to sail for a new world, seeking wealth, glory and power. The Soviets and Americans had similar motivation when they opened the frontiers of space.
In each case desire produced a bountiful treasure, even if the bounty found was not what the explorers were seeking. Ranging from agricultural gold of the New World to electronic gold of the Space Age, desire advanced civilization, and created wealth.
Now with the Nano Age upon us, exploration is taking us to the far reaches of smallness, cracking the codes of nature, creating the potential for discoveries to prolong life, minimize suffering, and believe it or not, to revolutionize paper.
According to Mihail Roco, who leads the United States National Nanotechnology Initiative (with a budget of about $1 billion annually), “Nanotechnology is ideally suited to help traditional industries become more efficient and competitive, advancing knowledge and emerging technologies.”
Roco, who delivered a presentation this past October at the first Nano Workshop for the U.S. Forest Industry, said the following, “Paper is a true composite of nano fibres, and other nanostructured materials. It stands to reason that nanotechnology will help produce better, more efficient paper, and addressing such areas of relevance as electronics, new structural materials, and maybe even addressing security concerns.”
Alexander Koukoulas, chief scientist with International Paper explained it this way, “We have been using nanoparticles as long as we have been making paper, but we have not fully understood how to utilize them.”
Koukoulas applauds the focus on nanotechnology, including the recent nano workshops, building awareness and encouraging fundamental research. In his words, “If government can appreciate the potential that the forest products industry can bring as a resource base, and get money into research groups, a lot can come out of it. It’s wise to focus on nanotechnology, because it captures the imagination and has the potential for being the next frontier.”
Power inside the sheet
Dr. Phil Jones, director, technology and new ventures for Imerys, said it this way, “Nanotechnology has emerged because we now have the tools to literally see materials at an almost atomic scale. Because many of the building blocks used in paper and board manufacture are nano-dimensional, we will benefit from the enormous amount of money the whole world is investing in nanotechnology. Our industry has been able to take advantage of the properties of natural materials and we have been able to formulate these components to advantage. Now we have the tools to see the true nature of these materials and will be able to deliberately fabricate new materials for new applications.”
Added Weyerhaeuser’s Del Raymond, director, Strategic Energy Alternatives, “The reason that nanotechnology fits so well with papermaking is that our industry is really a collection of industries, where each segment stands to gain from nano understanding of the fundamentals of nature and man-made materials. Thanks to computer science, and advances in physics and chemistry, we already manufacture more precisely and efficiently, and pollute less. Increasingly we can see the first hint of trouble on a microscopic, if not nano scale, and see it on-line. That’s a big advantage to control costs, and add value.”
Raymond, who also chairs the Agenda 2020 Chief Technology Officer’s Committee continued, “Apart from pulp and papermaking, our industry is a huge generator and consumer of energy. Nano advances, combined with our bio-refinery initiative, could make a considerable difference in boosting energy efficiency and improving environmental performance.”
Greg Bengtson, who leads the Compozil Select nanoparticle team at Eka Chemicals says, “There’s nothing blank about a blank sheet of paper, if you know how to see what’s happening inside on the nano level. Over two decades of intensive R&D have taken us to a whole new level in the nano-engineering of retention aids and polymers. Add to that the papermaker’s ability to design higher performance properties into the sheet-ranging from extreme smoothness to electronic tracking devices, and you will see the image and reality of high tech manufacturing overtake paper’s old-fashioned smokestack industry persona.”
Kurt Moberg, director of Strategic Business Development with Penford, claims that nanoparticle retention systems are becoming the norm across a wide range of grades, and now, even more effective as a tool to raise productivity.
Moberg says, “A new breed of highly cationic starches (up to four times higher charge than before) can be pumped right out of a tote. Effective even in SC, newsprint and deinked grades, they achieve a faster payback, reacting more robustly with silica, enabling more powerful the dewatering.”
Instruments that unlock mysteries
Essential to nano progress is the parallel progress with measuring and monitoring the unseen, and at some point to see it, figuratively or literally. Just as the Hubble telescope has helped to clarify blurry nebulae, instruments can help us to see into “inner space” in a profound way.
In the words of nanopapermaking pioneer Philip Hakansson, R&D director of Stora Enso Nymolla, “The paper industry is a fertile ground for nano creativity, because paper is a composite material, already employing molecular assembly techniques to build up a base structure, nano coat the base, and positively combine with inks, glue and so on. From the process of growing trees throughout pulp and paper manufacturing and converting/printing, nano has a role.”
Reading the web with near infrared
First employed to measure grain maturity at harvest time, and now in a developmental stage in pulp and papermaking (also breakthrough medicine, see sidebar), NIR (near infrared spectroscopy) provides on-line measurements at the wet end. On-line measurement is nothing new, but solutions are still needed for properties like roughness and hydrophobicity (water rejection).
Monitoring radiation in the wavelength spectrum between visible and infrared light (approximately 1,000 to 2,500 nanometers) begins with a halogen lamp, mounted directly above the web, emitting high-energy light that makes the molecules of the paper vibrate. The vibration causes electromagnetic radiation to be released. Radiation from the paper is reflected by a mirror, which directs the light into a fibre optic cable for transport to analytical equipment. The radiation that is captured functions as a unique “fingerprint” for the particular sheet, as it’s being made.
Said sa Martensson, leader of Stora Enso’s NIR project, “Printers will benefit from our growing knowledge of properties in the sheet. More precise data like surface smoothness, paper thickness, colour and tear strength will help printers know exactly how a specific roll or ream translates to in terms of tensile and dry strength.”
It’s clear the ability to “read” the paper web is increasingly important in making better paper, and building in desired properties. As the tools are developed to measure and control stickies, runnability will benefit and rejects will be reduced.
The basics of nano manufacturing
Essential to the nano industrial revolution is molecular manufacturing, which includes building from the nano level up to the molecular level.
This is then assembled into real products-like heart valves, super diapers, long lasting auto paint finishes, stain resistant clothing, ultra-thin paper coatings, and a growing range of materials, which set new performance standards.
According to many experts in the field, there are two basic approaches to building invisible manufacturing systems. Scientists refer to the top-down approach and the bottom-up approach. The top-down approach involves molding or etching materials into smaller components. This approach has traditionally been used in making parts for computers and electronics. The bottom-up approach involves assembling structures atom-by-atom or molecule-by-molecule, and may prove useful in manufacturing devices used in medicine. The assembly model is clearly the path for papermaking.
The nano necklace
Eka’s Joakim Carlen, manager in R&D for the polymer and nanochemistry group and Dr. Michael Persson, senior scientist for R&D, consider partnership with customers and universities to be essential to move nano science forward.
Carlen suggests that better techniques for characterization in the nano scale are allowing for further development and evolution of their Compozil Select nanoparticle retention system. The shift is from single nano spheres or balls to nano chains.
Persson indicates that by reducing the size of a 3-5 nm particle to an even smaller particle size allows you to increase surface area in relation to polymer flocculation.
Said Persson, “The way we are able to link nanoparticles together produces something like a pearl necklace. We can now closely control structuring. The molecule in the silica doesn’t change, but the way we direct the monomer to the right spot is what’s new.”
Carlen sights the fact that the strong bonds between each nanoparticle mean that high shear can’t destroy them. The bonded area is as much as half of the cross-sectional area of the 3-5 nm particles.
Carlen and Persson point to their close relations with Sweden’s Lund University, where much progress has been made in advancing nanotechnology. Said Persson, “Eka’s Compozil Select has evolved through cooperative work with universities, including Lund, where a cryo-transmission electron microscopy laboratory provides for analysis of nanoparticles frozen in amorphous ice. Another application is electron tomography, allowing for the construction of three-dimensional models of ultra-structural morphology.
One technique that Eka uses in cooperation with Lund University is the manipulation of nanoparticles through solution synthesis (such as silica nanoparticle sols) by reducing aqueous metal salts or metalorganic compounds. If the reduction is followed by the addition of a suitable organic molecule, the particles can be stabilized as the organic compound binds to the particle surface in solution. The efficiency of this is shown by the ability of the particles to be dried and re-dispersed, while maintaining their initial size and shape.
Nano coating formulations
Understanding of nano-dimensional features in coating structures will profoundly affect coated paper properties.
The thickness of kaolin platelets has always been important to coating, but now, thanks to the field emission scanning electron microscope and improved appreciation for crude mineral resources, coated properties can be improved by decreasing kaolin platelets to a thickness below 100 nm.
Dr. Tony Lyons, director of research for Imerys, Pigments for Paper, said, “Multi-pigment producers will partner more with papermakers and additive suppliers in the molecular manufacturing of the sheet, because minerals are both a platform and facilitator. Super coverage, super print gloss and super coating strength will result. Advances in the rheological properties of coating color will go hand-in-hand with improved paper properties.
“Totally new properties in paper will be limited only by our imagination. As we master nano engineering of size, shape and surface properties, greater prosperity will follow. The benefits from lower consumption of raw materials is obvious.”
It’s likely that joint ventures, or even mergers of supplier companies will produce in-situ polymerization of latex binders or in-situ conversions of natural binders. In-situ processing options offer the potential for dramatic decreases in binder usage, as they would be more efficient.
Adding to the scenario is the possibility of producing pigments with functional surfaces that interact with ink and light in new and better ways.
Links to inks
Coating formulations are adjusted to match printing inks today, based upon our comfort level on the micrometer scale, and adjusting at the micrometer level. So what does nano-scale know-how offer beyond current practices?
First, it’s the ability of nano-engineered products interacting with inks differently because of the dimensions of the pigment. Looking ahead, some predict that we may see that nano-scale adjustments in the size of pore features in the coating structure have dramatic effects on the ink and paper interaction. In addition, the ability to slow down or speed up the interaction of pigment surfaces, polymers and inorganic compounds will be of great value to manipulating ink functionality.
Receptivity of the surface to ink might be adjusted to making print mottle problems a thing of the past.
A potentially very exciting future is the merging of electronics and paper. Paper is basically a flexible display. The ‘what ifs’ for printed circuitry and screen displays are staggering. According to Ulf Carlson, director of R&D of SCA, “embedding miniature electronic brains into paper and packages allows an operator to point a scanner at a box out of reach, and know details about the outer casing, and specific contents within. Who could have imagined that?
In a similar way, why couldn’t a nano-brain tell us properties in a sheet? That’s certainly a new kind of retention aid — paper that not only prints better, encases or folds well, but holds knowledge.”
Concludes Lyons (with a big grin) on the nano magic of the future, “The Harry Potter moving picture newspaper and magazines may not be magic after all!”
Martin Koepenick of Innova International has been writing about paper industry innovation for over 20 years. Innova provides creative concepts and global editorial programs to industry suppliers and producers. Contact him at email@example.com
HUMAN BODY, PAPER BODY
The human body and the body of paper really have a lot in common. Each is built upon billions of cells from nature, forming into a multi-functional homogenous entity. This is not to say that you will be able to actually date the photographic image of the model you see in a magazine, but you can already dial a friend with a paper phone. And you can cure ills within your sheet, or prolong its shelf life with nano-engineering.
Nano-scale medical applications are close to being in production already, propelled by researchers Naomi Halas and Peter Nordland at Rice University in Texas. Nanoshell spheres for the treatment of cancer are made of layers of gold atoms wrapped around a microscopic silica core. Proteins, attached to the core, will go after tumor cells once the nanoshells are injected the bloodstream. The nanoshells will seek and bind themselves to soft-tissue cancer tumors. Once a few dozen nanoshells are bound to each tumor cell, the body will be scanned with near-infrared light, safely penetrating the body and illuminating and heating the shells to an intensity which will cook the tumor without destroying nearby healthy cells.
NANO IN THE FOREST
Cellulose fibres are made up of microfibrils which in turn are made up of nanofibres that are around 3 to 5 nanometers in diameter. The challenge is to liberate and stabilize them, as they offer a potentially high
-value raw material with high strength properties.
Paper and board are composite materials made up of materials that have some degree of nanodimensionality. Major programs underway in the area of nanocomposites will allow significant enhancements to paper and board as we know them, as well as developing new products.
Many nanotechnology programs relate to using self assembly of building blocks to produce novel structures and products. Indeed, a good deal of the early work on nanotechnology came from people working on biological materials such as sea-shells, bones and teeth. Wood fibres themselves are the result of a self-assembly process of the nanofibres into micro-fibrils. We should be able to learn from this and apply these techniques to lignocellulose systems.