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Summary of presentation made by Dr Mahendra Patel in the Seminar, explaining that Paper Industry could be a fertile ground for cultivation of Nanotechnology as the basic constituent of raw materials is cellulose- a glucoside chain with hydrogen molecules, which are of nano dimensions. Many new products and processes developed or under development thorugh Nanotechnology were discussed by Dr Patel.
Applications of Micro and Nanotechnology in Paper Manufacturing, a paper presented by Dr Mahendra Patel in Senior Management Seminar, in PaperAsia-2010, organized by UBM Trade Fairs, Singapore on the 17-18 June 2010.
Nanotechnology entered into public arena in 2001 in USA with formation of National nanotechnology Institute (NNI). USA spent 422million $ in 2001; 988 in 2005 and 1052 million dollars in 2006; presently, it is more than 3.7 billion dollars. The global investment on nanotechnology is arounf 5 billion dollars. The world demand for nanotechnology is likely to reach 90 billion $ in 2020. Thus progress and prospects of nanotechnology are enormous and paper industry cannot afford to ignore the possibility of benefitting from these developments. Paper Industry is considered to be a fertile ground for the growth of nanotechnology.
Areas where Nanotechnology has made access are:
GENETICALLY ENGINEERED TREES
1) In the raw materials, technology of GENETICALLY ENGINEERED TREES has gone to the
field from the laboratory now. In Brazil Aracruz Cellulose, Suzano and International Paper are all involved in research into genetically engineered trees. Suzano manages over 3,000 square kilometers of timberland in Brazil. It has partnership with Israel-based CBD Technologies on a project to increase the growth rate of eucalyptus trees. Regular eucalyptus trees are usually cut down after seven years, during which they grow to a height of 20 meters. Trees treated with CBD can reach that height in 3 years or less. International Paper, is also involved in GE tree experimentation. Recently, the Agriculture department of USA has approved plantation of genetically engineered trees.
2) Stock Preparation
Nanotechnology has found application in the Stock preparation since a decade or so. However, developments are still taking place along with improved nano-particles and measuring systems. A number of mills worldover claim to have been running their systems using micro-particle technology.
Increasing replacement of fibre by mineral fillers is of high economical interest as the fibre cost is about one third that of fibres. It also advocates for better environmental protection. This is the SEM micrograph of a sheet with superfilled paper; i.e. ash content exceeding 30%. It may be remarked that on understanding the fibre and mineral characteristics at micro and nano-level as well as their networking features, such fibre strength and bond factors in conjunction with sizing agents and other chemicals, it is possible to increase the ash content, maintaining
the drainage and runnability factors.
The micro-particles are bentonite and colloidal silica, characterized essentially by their large surface area per unit of weight. A nanoparticle weight of 5 grams, could represent up to an acre of surface area. Functional chemical additive usage could be reduced by 2 orders of magnitude Sheet ash could be increased by 5-10% at a higher level of sheet strength. Press section rewetting on a modern, high speed machine can be significantly reduced. The interlayer space of montmorillonite contains in the nature calcium ions, which are exchangeable and can be exfoliated into extremely thin plates. Theoretically, these plates can be as little as about 1 nm in thickness, yielding a huge surface area per unit mass. In practice, not all of the platelets will become separated from each other.
The first silica used was colloidal silica having a spherical shape with an average diameter of 5 nm, with a surface area of 500-800 m2/g and exhibiting a very high
anionic surface charge.
According to one method, fibrous cationic colloidal alumina micro particles and a polymer are introduced to a papermaking pulp to form a treated pulp having improved
A microparticle retention aid for use in papermaking containing a high performance purified natural zeolite pigment has been reported. When used as filler, the novel zeolite pigment is readily retained and eliminates print-through in uncoated papers. The novel zeolite pigment is low in abrasion and provides improved coefficient of friction. Recently, a new technology named as MICROPOLYMER TECHNOLOGY has been reported. It employs cationic and anionic micropolymers, which are synthesized using a controlled molecular weight cationic polyacrylamide polymerized within a coagulant matrix. The unique combination of molecular weight and charge density of the cationic micropolymers results in a highly efficient system with a different structure and composition
3) NANOPARTICLE-DRIVEN PAPER MACHINES
As silicate nanoparticle retention and drainage systems are very attractive, it is expected that most machines will use them in the future to derive a number of Benefits as shown in this slide.
It appears that nanoparticle retention and drainage systems are becoming more widely accepted and are even becoming more specialized. According to one industry estimate, there are over 1,000 nanoparticle-driven paper machines in use today. The most important property attribution is the retention and drainage, which leads to better runnability and fewer breaks, thus increasing the productivity. Better formation, dry strength and optical properties of the end products are made possible by nano technology. Increased production and reduced steam consumption are the tangible benefits to the mill.
4) CALENDER ROLLS
Nanotechnology has led to developments for improving the wear resistance, impact toughness, and surface finish of roll covers. Metso's new press section consists of PressJade D, W and F ceramic coatings that are engineered for specific paper and board grades. The novel nanomaterials technology behind the new PressJade improves the long-term runnability of centre rolls and cuts maintenance costs because of improved stable surface roughness and reduced wear.
The nanomaterial composition of the coating has boosted hardness and wear resistance by ~20% along with increase in impact resistance. The new coatings have therefore clearly better mechanical resistance against belt and felt incidents than earlier systems. The special microstructure makes the coating material hydrophilic and anionic, contributing to a clean roll surface and easy doctoring. Practically no release chemicals are needed with the new PressJade coatings.
The new coating raw material is a special ceramic-ceramic nanocomposite. The chemical composition and phase structure of the raw material and its micro porosity are based on a precise formulation. This has led to a unique combination of coating properties that could not be achieved with traditional materials technology.
Nanopearl was recently developed by Voith, which has advantage over all other traditional products with lesser cost and lesser power consumption .The nanopearl filled paper has unrivalled quality.Slide showing Nanopearl covers with nanotechnology fillers.
5) Fillers and Pigments - NANO PRODUCTS FROM KAOLIN
Previously, conventional kaolin products tended to have particles of many unknown sizes that used to filled up the empty spaces. This masked the benefits made possible by mixing various shapes. Today, narrow particle size distribution kaolin from Middle Georgia, England and as-mined Brazilian clays are offering new possibilities in coating engineering. This makes it possible to use technologies developed in the world of liquid crystals and colloid chemistry, for example, to allow a self-assembly of the components to take place.
Understanding of nano dimensional fea¬tures in coating structures will profoundly affect coated paper properties. The aspect ratio, specifically the thickness of kaolin platelets has always been important to coating. With the help of high resolution Field emission scan¬ning electron microscope and improvised systems for crude mineral resources, coated properties can be improved by decreasing kaolin platelets to a thickness below 100 nm. Kaolinite clays and other pigments prepared in nanoscale is the base for nano engineered products.
The AFM image exhibits the atomic structure of kaolinite clay mineral, where the atomic units (0.535nm), schematized in the right hand side, can be clearly seen. So far, we had not directly seen the hexagonal units of kaolin. This image has just been produced and in due course, we will have number of such views, leading to nano-phenomena beyond our imagination. GCC is a typical example of producing fine materials by top-down method by fine grinding of the natural mineral such as marble, chalk etc. On the other hand, PCC is synthetically prepared, approximating to the bottom-up method and thus there is possibility of controlling the particle size and brightness etc. Nano product of talc, platy in morphology with specific surface area of 270 m2/g and average particle size of 70-120 nm (0.07-0.12 µm) have been produced, having enhanced properties.
PACKAGING area has benefitted the most on application of nanotechnology. Better and more specific performance of barriers and protective coatings in packaging materials and addition of functional properties, such as sensory and anti-microbial qualities, are important features for food packaging. Improved barrier properties may be obtained by the use of clay-based nanocomposites as films and coatings.
Developments made recently in nanotechnology for packaging are:
Metallic/ceramic nanoparticles (carbon nano fibres) to combine light weight and strength for both equipment and structures.
Self-assembled monolayers to offer functionality in single layers, thus obviating multilayers and their vagaries.
Nano bar codes.
Encoding or decorating individual surfaces.
Counterfeit protection, especially for high-value consumer products, using nanotaggants.
Nano crystalline indicators to sense and signal modified-atmosphere environments within packages.
Light-activated oxygen-sensing inks.
Food deterioration sensors.
Power for intelligent packaging, such as radiofrequency identification (RFID).
LSA Authentification system
The LSA system (Laser Surface Authentication system), launched by Ingenia Technology Ltd based on the process developed by Imperial College in London and Durham University recognises the inherent fingerprint within paper, plastic, metal and ceramics.
The LSA system tries to identify the equivalent of a fingerprint, iris-scan, or other biometric of a document or packaging, for item-level self tagging and then base this biometric on naturally occurring microscopic randomness that cannot be controlled by anybody. The next step is to read the random biometric and store it in a database (Fig.16) followed by verification of the authenticity, reread the fingerprint and compare it with the database original (closed loop authentication). Additionally, the fingerprint can be cross-referenced with other information or
A new kind of nanopaper stronger than cast iron and tougher than bone has been reported, which could be used to reinforce conventional paper, produce extra-strong sticky tape or help create tough synthetic replacements for biological tissues.It can be used to make tough packaging material, filters, membranes, and even car and aircraft parts and medical implants.
8) Conductive paper
A layer-by-layer assembly of poly (3,4 ethylenedioxythiophene)-polysterene sulphonate (PEDOT-PSS) on lignocelluloses wood microfibers was used to make conductive fibres and paper. The conductivity of microfiber increased linearly with increasing number of bilayers of PEDOT-PSS. The measured conductivities ranged from 1 to 10 S cm-1. The nanoprocessing of soft wood fibre is shown in the figure.The fluorescent images of the longitudinal and cross-sectional faces of nano-coated fibers. The PAH coated both the outside surface and the inside lumen surfaces (green positively charged coating, red - negatively charged coating, layer thickness is 80 nm or 0.08 micrometers). Left images are longitudinal confocal faces, the right images are transverse confocal cross-sections of nano-coated fibers. The Scanning electron microscope (SEM) images of pre-formed white-office paper (left), and same paper nano-coated with 2 wt % of magnetic nanoparticles (right) are
shown in this slide.
9) Tissue paper
Tissue paper contains micro structures which are vital for the overall properties, namely bulk. Here are the X-ray photoelectron images of coated tissue showing presence of Silicon in trace amount, embedded in the fibre surfaces.
10) Antibacterial Paper
Some paper and other products incorporating inorganic antibacterial agents are already in the market. Antibacterial paper has a promising future as it can serve for arresting the Hospital acquired infections.
A new process, termed as Substrate mechanism, has been reported for formation of silicon carbide whiskers from rice husk and oxides such as alumina and titania as well as aluminosilicates starting from agro residues. The process consists essentially of forming insitu the oxides inside the fibre lumens, coking at about 500°C and then pyrolising at elevated temperatures (1500-2000°C). The SEM and TEM of the SiC whiskers formed from rice husk are shown below. Nanotechnology is pervading fast, proving itself to be a revolutionary technology with promises to change totally the manufacturing process and bring all-round developments of the society-fulfilling the theme of this conference-Sustainable Growth for a Sustainable world.
Dr Mahendra Patel
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