Monday 19 November 2007

A resurgence of regenerated cellulosics.

In the last 2 years, massive expansions in viscose production, and the pulp required to produce it have been announced – totalling in excess of half a million tonnes of new fibre. Surprisingly none of the expansion involves the more eco-friendly lyocell route. In the absence of this new capacity, viscose and lyocell prices have risen sharply and the market is currently undersupplied due to high demand in textiles as well as nonwovens. The world’s leading producer, Lenzing is enoying full production and good prices. 2007 will be its best year ever, and they are leading the expansion.

(Source: The Saurer Report 2006-7)
Research into cellulose and its derivatives is increasing. To take a few highlights from recent conferences:
  • Processes potentially capable of giving low cost cellulosic nonwovens are now being evaluated on a pilot scale at TITK and Fraunhofer.
  • At TITK, Lenzing and Nanoval are co-operating to produce a “melt-blown” version of lyocell using the Laval nozzle to split the fibres into micro-fibres.
  • At Fraunhofer, Weyerhaeuser and Reicofil are using a 60 cm Reicofil melt-blowing nozzle as a spinnerette to produce spun-laid lyocell.
  • These processes work with low-quality dope from paper-pulp and the cellulose can be more easily alloyed with high levels of other materials such as PP.
  • Ionic liquids have made dopes with 20% cellulose from which Tencel-like fibres and alloys with other polymers have been spun on lyocell pilot equipment.
  • 30% solutions of cellulose carbamate in NMMO have been converted to fibers with tenacities above 60 cN/tex. (These solutions are anisotropic above 20%)
  • Cellulose nanofiber fiber webs for use in medicine and cosmetics have been produced by the surface culture of bacteria.
  • Cellulose nanofiber webs made by electrospinning appear to have a total free absorbency of 2000 gms/gm.
  • Work continues on the dissolution of enzyme degraded cellulose directly in caustic soda.
Could cellulosics really replace polypropylene as the workhorse fibre for disposable nonwovens?
As we have seen, the ecological logic is sound:
  • Cellulose is the only really abundant fibre-forming polymer produced and disposed within the carbon cycle. (but don’t forget alginic acid and chitin remain to be fully exploited.)
  • Pure cellulose in the form of cotton, grown organically maybe in Africa, has the least environmental impact of any fibre and would be a low-cost yet valuable crop.
  • If cellulose must be grown on land which can not be used for food crops, it must first be pulped, dissolved and regenerated to form useable fibres.
  • Numerous processes exist for making cellulosic fibres from biomass, and all are potentially carbon-neutral because the parts of the biomass unsuitable for including in the finished fibres can be used to power the pulping, dissolution and fibre spinning operations.
  • Existing dry-lay, wet-lay and air-lay nonwoven process could convert these fibres into nonwovens provided hydroentanglement is the bonding system.
  • Surface acetylation of cellulose fibres can allow some thermoplasticity for thermal bonding purposes if the extra small monetary and ecological expense can be justified. (Acetic acid is a by-product of the pulping operation.)
  • Cellulose can be spunbonded, literally, in various ways to make self-bonded nonwovens, or spun laid where hydroentanglement would be the bonding mechanism of choice.
  • Assembling finished disposables without the help of thermoplasticity would be tricky, but fabrics can be glued or even stitched together – by computer-controlled high pressure water needles - in the same way as these needles at even higher pressure are used as cutters.
  • Cellulosic fibres can be converted into superabsorbents, and such products are already used in wound care. (Cellulosic nonwovens could be treated on one side to form a self-sealing breathable backsheet.)
  • Cellulosic disposables would be fully compatible with sewage systems, especially if the fibres are short and lightly bonded, or if the products are shredded through a waste disposal unit attached to the toilet.
As an aside here, any biodegradable waste could be disposed of through shredders into the sewage system and anaerobically digested at the sewage farm to yield methane for power generation.
  • Maybe as new infrastructure is developed and old infrastructure renewed, the installation of this option would take a load off landfill and the reduce the environmental costs of collecting and transporting rubbish from homes to landfill or aerobic composters.
  • If organic matter – including urine and faeces – could be kept out of the solid waste, the collection of the remaining rubbish could be very infrequent.
  • The life cycle analysis of the disposable diaper could be improved. Diapers would be credited not just with the energy generated from their mainly cellulose construction but also with that from the excrement they have saved from the landfill.

In Conclusion

For the last 40 years, the dramatic growth of the nonwovens and disposables industry has depended on increasing use of fossil reserves. Consumers have accepted convenience products based on unsustainable, non-biodegradable materials requiring landfill disposal. Climate change and its effects are changing consumers attitude to disposables and the continuing oil supply/demand imbalance will encourage a reversion to polymers from biomass. Flushable disposables based on cellulose would be sustainable, and recyclable to energy in sewage treatment.
Calvin Woodings

Thursday 8 November 2007

Future Diaper Raw Materials?

While synthetic polymers account for only a small percentage of the oil usage, and could be obtained from coal or tar more easily than could transportation fuels, they will become increasingly costly to a point where the use of natural polymers and their derivatives will become viable again. Furthermore as consumers demand ever-more low-carbon-footprint biodegradable products based on renewable raw materials the case for such a reversion to the natural will increase.

Polylactic acid (an aliphatic polyester) has the undeniable advantage of low temperature thermoplasticity which makes it an excellent candidate for replacing polypropylene in existing nonwoven processes – whenever the price falls to parity with PP having taken the different polymer densities into account, i.e. on a cents per cubic centimetre basis. It currently sells at a premium into products where claims of “corn-based” “natural” , “sustainable” and “compostable” have value, and today this is mainly into packaging films and mouldings, wipes, coverstocks and textiles. The process used to make it does require more energy than a fossil-fuelled polyester and the current product alleviates this by carbon-offsetting. One could also argue that the naturalness associated with corn is compromised by its complete depolymerisation to dextrose followed by fermentation to lactic acid which is then polymerised to PLA. There is also the issue of the current process needing prime food growing acreage and intesive fertilisation. Future processes based on waste biomass will be significantly more sustainable in the long term.
Cotton is at the other end of the naturalness scale to PLA in that nature provides a finished fibre almost ready to be carded. Unfortunately current low-cost cotton production requires extensive petrochemotherapy and irrigation and current pricing depends on government subsidy. Furthermore, and unfortunately for nonwovens producers, it needs bleaching and special finishing if it is to be processed efficiently into absorbent products. The more attractive, sustainable and eco-friendly organic cotton with its lower yields even from irrigated agricultural land could remain far too costly and scarce for most nonwoven applications and for some time will be used primarily specialities and in high value fashion textiles. If however a subsidised expansion of organic cotton production could be part of some grander scheme, such as eliminating US cotton subsidies and reducing poverty in Africa then ethical cotton nonwovens could emerge as a more mainstream raw material. If future consumers realise that genetic modification is just a speeded up version of the natural process by which all life evolved, they may be more favourably disposed to the man-made version of GM now becoming capable of transforming our ability to live a carbon-neutral existence. Organic cotton production would be an immediate beneficiary of the new mind-set.
Other Cellulosics?
Genetic modification of trees and other biomass could likewise transform the quality and yield of cellulose from agriculture, and may even allow its efficient production from bacteria. For now, cellulose is produced in the cell walls of vegetation when sugars produced by chlorophyll-catalysed photosynthesis are polymerised by enzymes to form both lignin and cellulose. The industrial grade of cellulose used to make fibre comes from tree-farms, where specially chosen species can be grown from sapling to maturity in as little as 10 years. New trees can grow from the stumps of the cut trees, and this happens on marginal land, generally unsuitable for food crops and without the intensive use of fertilisers or pesticides. The best tree farms yield in excess of 2.5 tonnes of pure cellulose per acre per year. For comparison, cotton growing at its most intensive yields about 0.7 tonnes/acre and needs good soil. Using trees on an industrial scale can attract the wrath of environmentalists. This is of course no worse ecologically than non-intensive farming but it is important to put the usage of trees as a raw material into the correct perspective. Using very round numbers to gain an approximate impression of the impacts involved:· 100 billion tonnes of vegetation grow and decay annually on land. This represents about 12% of the planets total production of vegetation, the majority being produced in the oceans.
· 12% of this land-based vegetation is in the form of wood (trees).
· Of this annual growth of 12 billion tonnes of wood, a maximum of 4 billion tonnes is removed by man. Half of this is burnt, either as fuel or to clear land for agriculture. The other half is used by Industry. (Compare this with 6 billion tonnes of fossil reserves "mined" and burned each year.)
· Of the 2 billion tonnes of wood used by industry, half becomes timber in saw mills, and half is used raw.
· Of the 1 billion tonnes used raw, half goes into construction (pit-props, telegraph poles etc) and half is converted into pulp and chipboard.
· Of this 0.5 billion tonnes, 0.4 billion tonnes of wood become wood-pulp for the paper, board, fibre, film and chemicals industry.
· A significant proportion of this pulpmill feedstock (up to 40% in some areas) comes from forest thinnings, and saw mill waste and 6% from non-pulp sources such as straw, bagasse, hemp and cotton. This feedstock yields about 0.25 billion tonnes of pulp.
· About 0.004 billion tonnes of this pulp output are a high quality dissolving grade for forming into fibres, films, water soluble polymers and chemicals. Dissolving grade pulp is perhaps better described as industrial grade cellulose polymer, and should be considered alongside the polyester or nylon polymer chips which are the feedstocks of the synthetic fibre plants.
· Rayon manufacture consumes 0.003 billion tonnes of this cellulose, with about 2/3rds going into staple and one third into filament and tow (including acetate).
· If ever the use of trees to make fibres on this scale becomes unsustainable, we could always farm the oceans for seaweed and make the closely related alginate fibres, or even produce chitin fibres from insects or shellfish.

So, the cellulose fibres, which thrived before we learned how to make fibres from cheap petrochemicals can thrive once again as the price, both monetary and ecological, of unsustainable raw materials increases further. Since the development of efficient hydroentanglement bonding processes, they can be converted into pure, soft cellulosic nonwovens which at first sight could provide consumers with the ecofriendly biodegradable nonwovens they
Unfortunately they are not thermoplastic so conversion processes will need adapting, and they are not yet available in the form of spunbonds so the cost differentials c.f. polypropylene spunbonds will be higher. Furthermore they are inherently wettable and will need finishing with hydrophobic materials to allow them to achieve the surface dryness levels needed for diapers. These problems are soluble.. After all, about 40 years ago polypropylene was thought by some to be incapable of replacing rayon in diaper coverstock because it was impossible to card, and far too hydrophobic for coverstock use.

Wednesday 31 October 2007

Elmarco Nanofibre Conference: Prague 17th -18th October 2007

Key Points

• Electrospinning (espinning) appears to be moving into the mainstream through its ability to create sub- 1 gsm fibrous layers with high functionality due to the very high surface areas achieved.
• Centrifugal spinning of 0.1 to 0.7 micron fibres from commercially available paint sprayers is possible. Fibre sizes are more variable than from espinning but the process is simple and relatively easy to scale up.
• Needleless espinning from rollers rotating in polymer solutions is allowing a wide range of nanofibre types to be produced at far higher productivity than the original needle process. Elmarco's pioneering work in this field is attracting much interest.
• Elmarco is now collaborating with Oerliken-Neumag on a production line for sound absorbtion materials, and with Alltracel on nanopeutics and tissue engineering. Swiss private equity has now taken a 26% stake.
• Elmarco are continuing contract research, selling the technology, selling laboratory test machines, doing commission coating with nanofibres and developing antimicrobial products. They continue to seek partners in specified market and technology areas.
• Chitosan, alginate, and collagen can now be converted into nanofibres using the roller process, and many hygiene and biomedical applications become possible.
• A PP nanofibre layer can make a surface super-hydrophobic, and a PVA nanofibre layer can meke it superhydrophilic.
• Cross-linked water soluble polymer nanofibres (Nano-superabsorbents?) can be made.


This predominantly academic meeting, to Elmarco's surprise, attracted 140 visitors from all over the world. The papers were generally good, but the printed papers from the Universities often bore little resemblance to and contained less information than the slides presented.

Techniques, Functions and Applications

Prof Joachim Wendorff of the Phillips University in Marburg ( Germany ) illustrated the wide range of espin research underway with a collection of slides not available in the printed text, and some from unpublished papers:

• 5-7 nm PLA filaments
• Barbed PLA filaments
• Porous PLA and polycarbonate “honeycomb” nanofilaments
• Beaded polyethylene oxide filaments
• Composites of PLA nanofibres and Polyamide ribbon filaments
• Bicomponents with enzymes, proteins and viruses in the core.
• Hollow carbon fibres obtained from polyacrylonitrile nanofibres.
• Superparamagnetic hybrid nanofibres based on bico, PLA sheath with iron oxide-loaded PP in the core.
• Copper nanowires from copper dinitrate in polyvinyl butyrate (converted to copper oxide by pyrolysis and copper by reduction in a hydrogen atmosphere at 300 o C)
• Green fluorescent protein which maintains its fluorescence (indicating its structure is intact) in the core of a bico nanofibre.
• Micrococcus luteus bacteria which maintains its viability in the core of a polyethylene oxide nanofibre. (E coli fails to reproduce after spinning).
• A 20/80 PLA/PEO nanofibre (400nm diameter) had had the PEO dissolved out to make a sponge fibre with high absorbency and a density of 0.2 g/cc.

Applications in homogeneous catalysis, tissue engineering, inhalation therapies, agriculture and oceanography are being developed.

• Catalysts when immobilised in the core of a polystyrene nanofibre allow synthesis of compounds completely free of the catalyst. 100% recovery of the catalyst is possible. (Scandium triflate mentioned as the catalyst for a Aza-Diels-Alder reaction).
• Growing stem cells on a chitosan/collagen nanofibre nonwoven scaffold until they differentiate. They are then used for implants. Oriented nanofibre webs are used to grow oriented muscle and bone tissues.
• Inhalation therapies are based on the ability of ~200nm-long nanotubes loaded with drugs (RNA and glucocorticoides mentioned) to penetrate deeper into the lungs than particles of the same diameter (this is what asbestos fibres could do.). Cutting the filaments to 200nm had been a challenge, but was now done with lasers.
• Water-resistant fibres can be spun from water emulsions of polystyrene latex: the PS nanosheres forming a water repellent surface.
• Hand-held espinning guns have been developed to spray nanofibres directly onto wounds to aid healing.
• Electospinning heads were being towed behind a tractor to cover crops in a “spider-web” of pheromone-loaded nanofibres to protect them from pests.

Prof Wendorff commented that scale-up issues were now the key development area, and waved a large, apparently heavyweight sample of nanofibre nonwovens (around 2 m long by 1.5m wide) to indicate progress was being made. Asked about current production rates he said his large sample took about a minute to make, but fibre speeds at laydown were about 50 m/sec. Solvent removal, even water, was not an issue. The surface area was so great, the fibres were dry before they reached the conveyor. As an aside he commented that Freudenberg have been spraying nanofibre polyamide from formic acid solutions for over 20 years.

Espinning Molten Polymer

Paul Dalton of the University of Southampton (UK) claimed this to be an under-researched area with only 10 papers published since 1981. He was working on this route for biomedical applications, earlier work having focussed on filtration, breathable barriers and tissue engineering. For tissue engineering, cell cultures are sprayed with a nanoweb which forms a scaffold to direct further growth. Because solvents tend to be toxic and kill the cells, he uses a polypropylene melt, the viscosity of which has been reduced to “treacle-like” (i.e. higher than the “honey-like” solution viscosities). He claimed to get down to 1-2 micron fibre diameter when spraying onto a single collector, and down to 0.25 microns when making aligned nanofibres by spraying into the gap between two parallel collectors. Here draw-down caused by stretching between the plates caused the further reduction. (The illustrative slide showed fibres from 190nm to 50 micron in diameter).

Comparisons of solution espinning of polyethylene glycol/poly caprolactone block copolymers with melt spinning the same polymer at 10 times the viscosity showed that good quality solid fibres could be produce, but only at about one-twentieth of the productivity. Melt spinning gave benefits in more controllable focussed fibre laydown but only at the critical temperature which might cause degradation. Solvent espinning gave unfocussed laydown but did not degrade the polymers. Varying the relative size of the PEG/PCL blocks in the polymer allowed a wide range of hydrophilic/hydrophobic behaviour to be obtained.

Nanosurface Engineering

Prof Akihiko Tanioka of the Tokyo Institute of Technology (Japan) positioned nano-surface engineering amongst the other surface sciences and defined a nanofibre as having a diameter less than 100nm and a length to diameter ratio of more than 100 – considerably more stringent than those claiming nanofibres from melt-blowing. Nanowebs made from such fibres have pore sizes below 100nm also, can become effective virus filters. His laboratory is working on a variety of applications for electrospun nanofibres:

• Ion exchange materials, either cationic or anionic with colossal surface areas. These could be for making ultra-pure water for semiconductor processing, or for purifying pharmaceuticals or biological products. For cationics, the polymer would be sulphonated, and for anioics, quats could be added. Catalysts could be added to create highly absorbtive materials with high catalytic power. Polystyrene spun from 10-17% solutions in THF/DMF was preferred for cationics, and poly-4-vinyl pyridine spun from ethanol/water for the anionics.
• A bipolar composite of both anionic and cationic nano-webs with a third unspecified ionexchange membrane in the center was being developed for electrodialysis of water to give improved efficiency of hydrogen production. It also allowed the direct production of acids and bases without bi-products.
• Aligned nanofibres of hydrophobic acrylics gave super hydrophobicity when sprayed onto a surface and the equivalent hydrophilic acrylic resin gave a more hydrophilic surface, both with reference to a cast film control. In the hydrophobic example, a random web had a 92 o contact angle and the same polymer parallel laid had a 130 o contact angle. Applications in textile finishing were sought to replace fluorochemicals with microstructured polyolefins. (148 o contact angle was the highest so far)
• Protein chips were being prepared by espinning a purified solution of alpha-lacalbumin from cows milk, followed by crosslinking it with glutaraldehyde. No further details provided.
• Nano-tubes were being used to make a microtubular fuel cell for micro-power sources. The nano tubes were espun from a coaxial bico needle using Nafion in a sol-gel precursor for the sheath and mineral oil in the core. Removal of the mineral oil yields a hollow fibre with a 2 micron outer diameter.
• Aligned nanofibre webs which diffract light to create colours without dyeing are under development.
• Flexible webs of carbon fibre are made by carbonising blends of phenolics and PAN chosen to give the best balance of strength and flexibility. Electrodes for batteries and capacitors, catalyst supports, sorbents and reinforcements were targeted. Fabrics with a density of 0.15 g/cc and a surface area of 500 m2/gm had been made so far.

Factors affecting fibre formation

Dr Tong Lin of Deakin University ( Australia ) has studied the formation of PAN nanofibres spun from different concentrations in dope, over various field strengths and collection distances, and with and without the use of an ethanol coagulation bath on the grounded electrode. He also used high speed video to investigate the draw down process and assessed the number of non-fibrous beads in the final web. He concluded:

• 7% dope is better than 5%
• The ethanol bath improves formation and reduces beading.
• The depth of ethanol affects the field strength at its surface, so higher voltages are needed to compensate for deeper baths.
• Finer fibres and fewer beads were obtained at the higher die-collector distances (10 cm much better than 2 cm)
• There is a 400:1 draw-down in the first 2 cms after leaving the nozzle.

Nanofibre Yarns

Marjeet Jassal of the Indian Institute of Textiles ( Delhi ) has been spinning PAN nanofibres into the gap between two conveyors, sometimes through a rotating annular magnet to insert false twist, and sometimes through an intermediate annular electode which was said to improve filament alignment. Both of these claims were hard to understand as only a single filament was present at this stage of the process. Both the verbal descriptions of the equipment and the slides were unclear. She was however positive that the electric field had to be twice the normal strength, this being achieved by the conveyors being at an equal but opposite voltage to the nozzle, and not simply grounded as is usual. While at one point 8% PAN appeared to be the best concentration, at the end she claimed 22% PAN spun into a 70C chamber with a field strength of 36kV. The resulting “yarn” collected from the conveyor is too delicate and shows too high surface friction ever to be used in a textile process, so reinforcement is the suggested application. The longest yarn produced to date? 10 inches.

Engineering and Medical Nanofibres

Masaya Kotaki of the Kyoto Institute of Technology ( Japan ) described the Nanon laboratory scale electrospinner developed by MECC Co. Ltd. This produces an A4 size sheet of web on a rotating cylinder in a sealed chamber. The rotational speed of the cylinder defines the orientation of the fibres and SEM's of a range of random to fully oriented results were shown. The webs could be removed from the cylinder on a cardboard frame. So far he had made webs from:

• Porous nanofibres which looked like an open-celled foam and must have a very high specific surface area.
• 10nm nanofibres
• PCL nanofibres loaded with 75% calcium carbonate
• Hollow fibres and hollow nano-beads.
• Epoxy, polyimide and polyaniline nanofibres.
• Bico nanofibres with a polyaniline core and a poly methylmethacrylate sheath. The bico route allows non fibre-forming materials to be espun if they can be inserted into a suitable sheath.

He has also measured the tensile strength of single nano-filaments made at cylinder surface speeds between 70 and 700 m/min and has shown that this speed change causes a big increase in orientation which can be further enhanced by hot drawing. The as-spun (700 m/min ) PLLA single filament broke at a stress of 175 MPa and a strain of 0.5mm/mm compared with 65MPa/1.6 mm/mm at 70m/min. Nozzle sizes have been reduced from around 0.1mm to 1 micron to further improve orientation.

Target applications were coatings for stents (to reduce porosity), electronic devices and sensors, and a filter receptor for spectroscopic analysis, the latter being used to carry liquids into FTIR analysis where the high transparency of PAN allowed good spectra to be obtained.

Espinning Emulsions

E. Klimov of BASF ( Germany ) explained how aqueous dispersions of polymers from emulsion suspension polymerisation could be espun into water resistant nanofibres. The polymer emulsion was first thickened with a water soluble polymer, preferably one with some fibre-forming capability, and then espun. The polymer particles coalesced as the water evaporated, then deformed and finally their surface molecules interdiffused to form a coherent, if fragile, fibre. 50nm emulsions could give 200nm fibres while 160nm emulsions could give 500nm fibres. The best fibres are obtained when the spinning temperature and the Tg of the polymer were matched, but cross-linking is also needed to increase strength and thermal stability. To achieve this allylmethacrylate is added as a co-monomer. Asked for the ratio of emulsion to thickener, Mr Klimov said they were spinning dopes with from 1 to 20% of emulsion solids.

Disruptor™ Nanofibre filters

Rodney Komlenic VP Business Development of Ahlstrom Filtration (USA) described their use of nanoalumina, in reality the naturally occurring mineral boehmite - AlO(OH), the major constituent of bauxite – as a filter aid. The mineral is refined using a proprietary technique into nanofibrils said to be 2nm in diameter and 250nm long. These fibrils have a specific surface area of 500m 2 /gm and are grafted onto microglass and wet-laid to make depth filters 0.8mm thick, with an average pore size of 2 microns. The filter papers have 42,000m 2 of nanofibre surface per m 2 of paper.

The fibrils work well in water between 5 and 9 pH where they develop a “huge” electropositive charge and can attract particles which would normally miss an uncharged fibre by a micron. This means that the 2 micron pore size paper can filter out submicron particles with minor increases in pressure drop. Log 3 reduction values for removal of 27nm MS2 phage virus had been found and Log 4 reductions of 300nm bacteria (Diminutia) and cysts (simulated by 3 micron latex spheres). They are also capable of absorbing dissolved heavy metals such as copper, lead and iron. The main application envisaged is as a polishing filter for drinking water. Having hydroxyl functionality it can attach to cellulose and can be formed into 3D filters using the “egg-box” techniques. 32% of Boemite is typically added to the filters. Powdered activated carbon (27 micron) can also be added to the paper to remove halogens and soluble orgainics without reducing the filter's efficiency at removing viruses.

Apparently sensitive to the fact that asbestos used to be fibrillated into nanofibres for filters, Mr Komlenic was keen to point out that the nanofibre emulsion version of Boehmite, “Alhydrogel” is approved by the FDA for use in formulating vaccines to treat diphtheria, tetanus, polio and pertussis. It is also commonly used as a thickener for gastric medicines and tablets. Asked about Boemite particles in the filtered water, they could be found, but only during the initial flushing out process.

Cabin Air Filters

Nico Behrendt of Helsa Automotive GmbH ( Germany ) mentioned their continuous bipolar nanofibre coating process used to treat both sides of a nonwoven simultaneously while being very cost effective and allowing great flexibility of polymer. The process was not described in any detail but from the schematic shown, it used a dip roll to pick up the polymer solution, this being scraped off the surface by a charged doctor blade, the other edge of which provided the electospinning edge. The benefits of the process were illustrated with reference to filtration efficiency versus pressure drop on cabin air filters with various coatings. At a mid-range pressure drop of 20 Pa, state of the art cabin-air filters were 25% efficient. This could be increased to 45% using single side coated uncharged nanofibres, and further to 65% with charged nanofibres. Their bipolar process, presumably with the electrical charge gave 90% efficiency at the same pressure drop.

Ion Exchange Nanofibres

Ludek Jelinek of the Institute of Chemical Technology (Czech Rep.) has been collaborating with Elmarco on producing ion-exchange nanofibres using the Nanospider equipment. Polystyrene was espun onto a PP spunbond, its stability increased by cross linking to allow mild sulphonation using 80% sulphuric acid at 25C for 5 minutes. Stronger sulphonation dissolved the nanofibre. Unfortunately the ion-exchange properties were too weak for industrial applications, so work continues with other polymers. Polymethacrylates, cellulose and chitosan were mentioned. Chitosan itself can adsorb heavy metals but uncrosslinked it dissolves in acids. It can however be phosphorylated and functionalised with other chelating groups.

Inorganic Nanofibres

Vit Chudoba of Elmarco (Czech Rep.) described Elmarco's development of inorganic nanofibres for electrochemical devices (batteries, capacitors, fuel cells etc), composites, thermal barriers, water purification and catalysts. The additives used, presumably loaded into a polymer solution were elements such as copper, carbon and nickel; metal oxides (NiO, TiO 2 , ZrO 2 , and CuO); ceramics (SiC, SiO 2 , Al 2 O 3 ) and spinels, particularly lithium titanate. The lithium titanate nanofibre webs were for anodes of high power Lithium ion batteries, the metal oxides were for composite reinforcement or thermal insulation, and the TiO 2 was for photocatalysis where the sub-500nm fibres had a surface area of 40-60m 2 /gm and outperformed Degussa's P25 TiO 2 powder.

Solvent-free electospinning

Wiebke Voigt replaced Helga Thomas of the German Wool Research Institute (RWTH Aachen - Germany ) to talk about espinning water solutions of polymers. Clearly the waterbased process gives water-soluble nanofibres, and to be useful these have to be stabilised by cross-linking. Presumably this yields a nanofibre superabsorbent intermediate, but Ms Voigt did not mention this.

• Lupamine, a poly(n-vinylamine) from BASF had been modified with BHBP and MAC so that it could be stabilised by UV-induced crosslinking to give a fibre with intrinsic antimicrobial activity.
• PVA nanofibres had been stabilised by heat treatment. Versions with silver nitrate had been made for antimicrobial use.
• PVA in 50/50 blend with polyethylene glycol dimethylamine and spun at 15% concentration in water gave a water stable mixture of beads and fibres, less concentrations of PEGDMA giving better looking fibres with inadequate water stability.
• Silicon dioxide nanofibres (600 nm) had been prepared by spinning solutions via a sol-gel process with tetraethyl orthosilicate as the precursor.
• Silica/PVA composites with a diameter of 380nm and excellent water stability had also been made.

Needleless Espinning

David Lukas of the Technical University of Liberec (Czech Rep.) pointed out that liquid surfaces deformed into multiple tiny cones when subjected to a strong electric field, and if the liquids contained polymers this deformation could lead to fibre formation. This was the basis of TUL's spinning of clouds of near invisible nanofibres from the surface of a smooth roller rotating in bath of polymer solution, a process which was now being commercialised by Elmarco and is the reason for the conference. Mr Lukas explained the physics involved in incomprehensible detail.

Centrifugal Spinning

Martin Dauner of ITV Denkendorf ( Germany ) observed that while molten glass, pitch (carbon-fibre precursor) and Basofil have been converted into micron sized fibres by centrifugal spinning for many years, little work has been done using the process to make polymeric fibres. Commercial centrifugal sprayers (“Center Bells”) have been developed for paint and varnish application by Reiter (not Rieter), these being hand held with rotors running at 45,000 rpm. These have now been adapted to handle fibre forming solutions, and each head can process about a third of a litre of solution per hour to give fibres in the range 0.1-0.7 micron diameter. Each head has coverage of about one-third of a metre, and they can easily be lined up to make wider widths. Gear pumps are used for accurate polymer feed. Fibrous webs shown were:

• Polyethylene oxide nanofibres from a 5% solution in water.
• Polyimide nanofibres from a 15% solution in DMAC/DMF.
• Cellulose acetate spun into filters with ~1 micron fibre size from a 13% solution in acetic acid spun at 12 mls/min. 0.2 micron fibres were obtained from a 5% solution spun at 60 mls/min.
• Others claimed but not illustrated were polyurethane, PAN, PVA and PLA.

Compared with espinning, the centrifugal approach gave similar fibre sizes at higher productivity (0.5 kg/ claimed at this point), easy cleaning of spinning heads, and easy scale up by replication of commercially available heads. The downside? Filament diameter variability was higher and the system worked less well with solvents of low boiling point (80C minimum). Furthermore, fibre diameters below 100nm appeared impossible, and melts were too viscous to work. A 1.5 metre line running at 7 m/min was being planned.

Medical Applications

Gary Wnek of the Case Western Reserve University ( Ohio USA ) is growing cells on espun nanofibre webs. He has shown that the inherent charge on such webs attracts cells and encourages tissue formation. Random webs form random tissues (e.g for skin) and oriented webs form oriented tissues (e.g for muscles). The cells can be grown separately on the opposite sides of the web and eventually link up to form a bi-layer structure – like skin. Webs tried were listed as:

• Poly lactic and glycolic acids and blends.
• Polycaprolactone
• Poly(ethylene-co-vinyl acetate) and EVOH
• PVA and PVOH
• Collagen
• Elastin

Collagen nanofibres were particularly successful for skin regeneration because they mimicked natural collagen scaffolding and exhibited excellent cell infiltration. The best solvent for espinning collagen was hexafluoroisopropanol. Asked if nanofibres were really necessary, Dr Wnek said that it depends on the cell types. For cartilage, micro fibres are best: for liver cells, even coarser fibre are better. If the cells are much larger than the fibres, the fibres are incorporated in the cells. If the cells are much smaller, they grow on the fibre surface.

Multi functional scaffolds for retina regeneration were using suspensions (rather than solutions) of poly(lactic-co-glycollic) acid, the water phase carrying the MMP2 gelatinase protein. The protein domains could be seen along the nanofibres. Asked if the lack of transparency of PLGA webs was a problem, it was not. Once the cells had colonised the web, web opacity was irrelevant.

Elmarco Developments

Jana Svobovoboda of Elmarco R&D (Czech Rep.) described the work being done with chitosan, collagen and alginate on the Nanospider™ roller espinner to make antimicrobial and antiviral filters for face masks.

• Chitosan's haemostatic, bacteriocidal, fungistatic and antitumoric properties make it a natural for biomedical fabrics, but it has proved hard to espin on its own. Now, Elmarco has a patent on blending chitosan with a little (<10%) polyethylene oxide which makes it work better. PVA can also be used in this support role.
• Similary, sodium alginate has been converted into 50-250nm fibres using a PVA polymer support.
• Collagen too has proved difficult on the roller system, and needs a special solvent and support polymer. A successful combination to give collagen (>98.5%pure) nanofibres of diameters in the range 30-120nm is now patent pending.
• Nanospider™ AntimicrobeWeb™ uses a polyamide (6/12) structure of 100-700nm fibres with a basis weight of 0.4 gsm and an air permeability of ~60Pa to carry antimicrobials into a filter structure. Chitosan, and quats were the additives mentioned. Nelson Labs (USA) have tested face-masks using the web and found both viral and bacterial filtration efficiencies above 99.9%. S. aureus; E.coli; P. aeruginosa, C. albicans; A. niger and Penicillium aurantiogriseum were the challenges.

Applications in waste water treatment, HVAC filters, cabin air filters and cleanroom filters are now being sought.

1 O 2 from Nanofibres

J Mosinger of Charles University in Prague (Czech Rep.) is producing polyurethane nanofibre webs doped with 5,10,15,20-tetraphenylporphyrin (TPP) photosensitizer. The 2 gsm webs contain 0.12% of the TPP, which on exposure to light releases singlet oxygen, a highly cytotoxic bacteriocide at the fibre surface. E.coli can be grown on the webs in the dark, but exposure to light kills the colony and prevents further growth. Auto disinfecting, sterile materials are therefore possible. Asked how much light is needed to trigger the kill, Dr Mosinger said about 2 hours in daylight or half an hour under a 100w halogen lamp. What was the shelf life of the fabric? About a year if kept in the dark. How transparent was the web? 90%: it was only 0.03mm thick.

Electrochemical Storage Devices

Lukas Rubacek of Elmarco (Czech Rep.) has demonstrated that the Nanospider™ roller system can make lithium titanate spinel nanofibres (LTO) for use in batteries, capacitors and supercapacitors.

As an anode in a lithium battery, the LTO fibre allows higher potential leading to better safety than the conventional lithium ion battery which can ignite if the charging circuit malfunctions. It's theoretical capacity is 176 mAh/g (c.f. 300 mAh/g of the lithium carbide anode batteries) but it can be discharged and charged at much higher rates safely and without damage. 3 minute recharge times with a 5000 cycle life were quoted. So, high power rapidly rechargeable batteries which will not catch fire can be developed.

The very high surface area of the LTO webs also allows electrical double layer capacitors to be made at higher capacities with lower internal resistance.

Air Filters

Stanislav Petrik of Elmarco (Czech Rep.) has been investigating the effects of nanofibres spun from the Nanospider™ machine on the performance of cellulosic air filter media. He has discovered that the Relative Fibre Length, i.e. the number of kilometres of nanofilament per square metre of surface correlates well with filtration performance for a wide range of fibre sizes and basis weights. In fact RFL and Pressure Drop correlate better than Basis Weight and Pressure Drop, so image analysis to establish fibre diameter and RFL can predict filtration performance where basis weights in the 0.01 to 0.1 gsm range are much harder to determine. Filtration efficiencies of submicron particles is increased by >>100% while air permeability is only reduced by >10%.

Sound Absorbtion

Klara Kalinova of the Technical University of Liberec (Czech Rep.) stressed that here we were considering absorbtion, not insulation, of sound. Absorbtion, being the difference between incident and reflected sound, is very dependent on sound frequency for any material. Most absorbtion occurs at the resonant frequency of the material, in reality the resonant frequency of the free fibres in the wadding or nonwoven. The remainder of absorbtion occurs due to friction between the vibrating air and the fibres. Layered nanofibres work best, and if a density gradient can be set up sound absorbtion is further improved. As fibre size is reduced the resonant frequency falls, so the finer the fibre, the better the absorbtion of usually problematical low frequencies. An acoustic nanofibre is now being developed as part of the recently announced collaboration between Elmarco and Oerlikon-Neumag.

Aligning Nanofibres

Yousef Mohammadi of the Stem Cell Technology Company, Tehran ( Iran ) is using the dynamic gap electospinning method to precisely control the alignment of filaments in a nanofibre web. In this method the electodes attracting the fibres are two vertical rotating discs space about 10 inches apart below the vertically downwards extruding nozzle. Both discs are at the same voltage and the nanofibres align themselves between them. As the synchronised rotation of the pair of discs carries the aligned filament away from the forming zone they are collected on the surface of a drum rotating between the lower half of the electrodes. The text referenced an EU patent application. (no details)

Calvin Woodings

29 th October 2007

Insight 2007 – Amelia Island: 21-25th October 2007

Key Points

• Green consumerism is now “Media Sexy” and has become a self-generating topic: most climatic oddities being linked to our profligate use of non-renewables.
• Legislation to encourage the use of renewable, biodegradable materials, especially in disposables is expected, first in Europe and then in the USA .
• A 30,000 tonne/year cross-linked carboxymethyl starch SAP plant is under construction to allow diaper producers to blend this 82% bio-based product with conventional petro-SAP and claim improved bio-content.
• It may soon be cheaper to make “petrochemicals” direct from biomass in government subsidized bio-refineries.
• A genetic engineering breakthrough has allowed Metabolix to increase the yield of biodegradable polyester produced by bacteria from corn sugar. A 55,000 tonne/year plant is now under construction.
• Wet wipe costs could be reduced if hydroentangled fabric could be cut and folded without drying.
• Nanofiber layers will replace the “M” in SMS and allow lower basis weights. Hills Inc. also claim 8kg/m/hr of nanofiber will be achieved by new melt blow heads using high MFI polymers.
• Celanese are offering acetate cigarette tow and the processes used to spread and bond it as a new nonwoven process.
• Fameccanica are developing laser cutting and shaping, and maybe welding, for diaper and femcare production.

Natural Plastics

Holly Wilson-Jene of Telles (A 2007 JV of Metabolix and Archer Daniels Midland - USA ) introduced their Mirel™ biodegradable polymer made from corn sugar. This was said to arise from a genetic engineering breakthrough which had increased the yield of the aliphatic polyesters (polyhydroxyalkanoates) produced by bacteria from the sugar. It is currently being produced in a 12 tonne/month pilot plant adjacent to ADM's wet corn mill in Clinton Iowa , and a modular, easily expandable production unit (55,000 tonnes/year) is under construction and due to start up in late 2008.

The plastic is under development in 80 new applications, the first being for cast films, extrusion coating and injection moulding. It has already been certificated for municipal and cold composting and for degradation in the aquatic environment, both sea and fresh water. The Life Cycle Analysis shows an 80% reduction in fossil fuel use and a 200% reduction in greenhouse gases compared with petrochemical-based plastics. Mirel™ therefore has a negative carbon footprint: its production requiring 2.2 kg of atmospheric CO 2 per kilo of plastic produced.

Applications include disposable cups, lids and utensils because unlike PLA, it degrades as litter and gradually disappears. Other packaging and agricultural applications are foreseen.

The genetic engineering process can yield a variety of polymer attributes for a broad range of applications by inserting different genes into the genome of the production host. Properties range from polyethylene like, through polystyrene, polypropylene to polyester. During the 20 years of development of the Mirel process, 320 patents have been granted and more are expected. Metabolix has recently prevailed against a patent suit brought by P&G ( Germany ).

In response to questions, and as suspected, Mirel™ is in fact ICI's Biopol*, acquired and improved by Metabolix who claim to have raised the yield of PHA from 3% to 80% of the bacterial body mass. Furthermore:

• It is priced at 3 times current polyester price and is in high demand from brand owners and retailers who are keen to respond to the strong consumer demand for sustainable products.
• Shelf-life is not a problem.
• It has FDA approval for food contact use.
• It is being developed for fibers and nonwovens and these should be available in 2 years
• Corn sugar is not essential. Cane sugar can be used, and in South East Asia , palm oil would be used.
• The Clinton plant will be powered by biomass from “several sources”.
• The negative carbon footprint only applies up to the factory gate. Clearly when the product finally degrades, carbon neutrality is restored.
*Commericalised in the UK in 1991, sold to Monsanto via Zeneca and then to Metabolix.

A Natural Superabsorbent

Nicholas Nourry of Archer Daniels Midland Co (USA) introduced a new superabsorbent, BioSAP™, based on cross-linked carboxymethyl starch, to allow diaper producers to increase the bio-content of their products. Its physical characteristics (particle size, shape, hardness, density, colour and moisture content) were said to be nearly identical with polyacrylates. Absorbtion kinetics in a free swell test using 0.9% saline showed a similar curve to polyacrylates with 60% of its maximum capacity being reached in 2 minutes and 100% in 60 minutes. In prototype diapers, rewets with the BioSAP™ were 3 times as high as the reference diaper with polyacrylate after two insults but only 25% higher after 3 insults. Strike-through times were identical at the first insult but about 40% higher at the 2 nd and 3 rd .

Asked if gel blocking is a problem as it was in the original 1970's starch-based SAP's, Mr Nourry said it was not. The hard particles maintain their shape. How much product was available? A 30,000 tonne/year plant was under construction and would start up in March 2008. The biobased content of BioSAP™ has been assessed as 82% according to ASTM D6866-06A because the carboxymethyl groups were from oil-based sources: however they need not be in future. How did the product compare with the earlier pulp-based CMC's? The earlier products were soft and gel-blocked: BioSAP™ was hard. Price would be comparable with polyacrylates.

A biodegradable Future?

Anders Moller (Consultant) provided a personal view of the future of spunmelt processes, currently producing 1.725 million tonnes a year of nonwovens, 75% of which are for disposable products, 98% of these being made from polypropylene. The landfill disposal of the products made using these spunmelts has generally been regarded as unacceptable for many years, the lack of any convenient alternatives at almost any price having prevented any action to try to remedy the situation. Mr Mollers argued that this was about to change. Politicians and legislators were about to wake-up to the fact that biodegradable and sustainable nonwovens were now becoming available, but were not being provided, despite high consumer demand, because they cost too much. The solution? Vote-winning environmental brownie-points and higher tax revenues to be won by legislating to tilt the playing field against polypropylene and in favour of the biodegradables. A tax on polypropylene for disposables use would render about 90% of the world's spun-melt capacity in need of costly modification to allow biopolymers to be processed, but the few multi-polymer lines would be able to profit immediately from the new tax. This will happen, in Europe first and then in the USA , and now is the time to prepare. Asked if carded nonwovens would benefit, Mr Mollers thought they would, but only until the spunmelt sector got its act together and learned how to process biopolymers. How soon could the legislation be expected? Inside 10 years.

Biorefinery Products

Bob Makolin of Abba, Makolin and Waldron Associates LLC foresaw the time in the not too distant future when it would be cheaper to make chemicals directly in biomass refineries rather than from refining and cracking fossil fuels. R&D funding for developing biomass refineries was available from the US Departments of Energy and Agriculture, and tax incentives were available to encourage biomass use. In Michigan the “Wood to Wheels” program was producing fuel rather than polymers and engines were now being developed to get the best from such fuels. Other projects were underway in Tennessee and Louisiana .

At present ethanol from corn is the biggest biorefinery product, the USA being the world's largest producer – bigger even than Brazil 's biofuel from sugar cane production. Iowa alone produces 3.5 billion gallons/year of ethanol, but corn is not an ideal starting point for many reasons and the industry would not exist but for subsidies which now amount to 51 c/gallon. It takes 3 times as much corn to make a gallon of ethanol than sugar cane; corn is hard on the soil and needs regular fertilizing, and a corn-crop failure in the USA could wipe out the emerging industry. For chemicals and polymers, biomass would be converted into methane and then on to ethylene and propylene, but here better enzymes and catalysts were needed before viable processes would emerge. In the EU however, biodiesel from oil-seed is the main biomass fuel, and glycerol is a by-product of its manufacture. Viable routes from glycerol to other chemicals and polymers are more likely to be developed.

High Value Nonwovens

Arnold Wilkie, President of Hills Inc. described the five new things that would result in an explosion of new product.

High speed spunbonding with separate attenuation and quenching in an open system, could produce 0.6 denier PP spun at 7500 m/min. These machines would also be good for polyester spunbond.

Meltblow routes to nanofibres defined here as fibres with a diameter of less than half a micron could be made simply by reducing the throughput. Now new spinnerets with small holes produced by electrochemical etching would allow productivity to be improved. Etching would allow more than 100 holes/inch (up from 35) with diameters of 0.1mm (down from 0.35mm) with and an L/D of 100 (up from 10). New PP resins with an MFI around 1800 would be used to get the 0.5 micron fibres at 3 kg/hour/m. PBT fibres could also be used on this equipment. Bico routes to nanofibres also show promise. Hollow segment pie constructions are easy to split in hydroentanglement and when 37 islands of polyester spun in an easily soda-soluble polyester sea (PLA?), very fine, but not nano fibres are produced. Kuraray are now producing a 300 islands version which yields 400nm filaments with a tenacity of 3 g/den.

New Polymers and extrusion methods . The EastONE® copolyester from Eastman is readily soluble in warm water and will help the bico-nano route. EVOH is also water soluble and PLA is soda-soluble. New extrusion methods are required to handle these in a bico process so that they can be kept separate from the islands polymer until the last moment – to prevent gel formation.
Textile processing of spunbonds . The techniques used to produce artificial suede apparel and furnishing fabrics can be applied to islands-in-a-sea bico spunbonds, and two Asian companies are now selling strong and flexible suedes which started life as spunbond PA6/PE bico nonwovens. NCRC are investigating a similar process using an non-soluble sea polymer carrying 108 islands into a spunbond fabric which is then split in hydroentanglement.
Pixel fibers are islands-in-a-sea bicos where the islands are treated as pixels and pigmented to make make logos, bar-codes or dates and serial numbers. 4-color fibres are possible.

Bico fibres with soluble islands would give low density normal-sized fibres with many micro-tubes which might be usable in filtration or dialysis.

Asked if nanofibres could form the M-layer in an SMS spunbond, Mr Wilkie said it could and this was now being piloted at 1.7 m wide. Substantial reductions in basis weight were possible for a given barrier level. 2kg/m/hr throughput was now being achieved but a quadrupling of this was thought to be technically possible. Ribbon fibres made using a bico process were commercial in Japan in speciality wipes. Multicomponent fibres can be produced at close to the same productivity as single components. Hills Inc achieve 4000 holes/metre in a spinnerette used to make a fibre with 400 islands. With regard to health issues, nanofibre dust is being regarded as hazardous until evidence to the contrary is available. Could starch be used in the core of a bicomponent? Yes if its thermal stability was adequate.

Synthetic and Filament Diaper Cores

Don Young, Director of Commercial Development for MTS compared conventional products (P&G's Easy-Ups, K-C's Pull-Ups and White Cloud Training Pants) with their unconventional counterparts (P&G's Easy Ups with High SAP/Hot melt, White Cloud Soft-Fit Training Pant with filament core, and Daio's Goon with filament core.) The dunk/drain test, the Multi-Dose Liquid Acquisition test, the mannequin test in the side position, the rewet test and the spreading test were carried out on all products, and the results interpreted in the light of a detailed analysis of product construction.

• Goon was the most absorbent in the dunk test (15.6 g/g) against 12-14g/g for the rest.
• Goon and the White Cloud filament diaper did best in the MDLA, lasting twice as long before overflow started. Overflow levels were a quarter of those of the others and hence liquid retention was also best.
• Goon did worst in the mannequin test (47 mls to leak), probably because it does not use leg gathers. The other filament core diaper worked best (82 mls to leak) with the Hi SAP/HM Easy-Ups coming second with 67mls.
• The P&G products gave the lowest rewet, with the High SAP/HM best at 0.1gm, half the rewet of the conventional Easy Ups. The other products were comparable at 0.35 to 0.44 gms.
• Spreading tests gave similar results for all products.
• All products were comparably priced at retail, this indicating that the consumers were reluctant to pay a premium for the higher-performing filament products.
• MTS estimates of the manufacturing costs indicated that the filament-cored products were significantly more expensive to produce than the others. P&G's Hi SAP/HM was intermediate between the filament and conventionally-cored products.

Mr Young noted much activity in the pre-formed core area and argued that if SAP and fluff prices continue to escalate we may yet see a diaper producer switch over. He also noted recently increased patenting of foam based diaper cores and speculated that the reduced transportation costs of such products could be tipping the balance in their favor assuming the well known problems of competition with the SAP for fluid could be overcome.

Acetate Nonwovens?

Rene Neron of Celanese Acetate LLC described how he hoped their customers would develop new applications for an intermediate of the cigarette filter tip manufacturing process in nonwovens. For many years, about 600,000 tonnes per year of acetate cigarette tow has had its crimp deregistered and is blown out into a 10 inch wide ribbon prior to being sprayed with the triacetin bonding solvent and entering rod makers at speeds up to 600 m/min. Whilst others, your correspondent included, have struggled to enhance this process to make wider and lighter nonwovens, Celanese has hit on the idea that even for the 10 inches wide web, several potentially profitable nonwoven applications could be developed if customers could be persuaded to install the necessary equipment and develop the appropriate bonding systems. So they have launched Celaire™ “a new product and process to make a single layer highly absorbent nonwoven”. A machine to convert the tow into a 10” solvent bonded nonwoven would cost from $300,000 to $700,000 and would consume 0.3 kWh electricity per kilo of tow converted. The tow could also be bonded in any of the ways obvious to those skilled in the art, presumably at great capital and energy expense on such a narrow web. The nonwoven would be lint-free (at least until it was cut) and could be made from any tow currently commercial in cigarette filters. Mr Neron was quite clear that no changes could be made to their tow production to adapt it in any way to suit other end uses. Products where acetate tow might be useable were listed as:

• Cotton gauze replacement in swabs and dressings.
• Meat pads
• Filters
• Clean room wipes.

Asked if the mineral oil finish necessary for precision crimping and processing of acetate would be acceptable in the target end-uses, Mr Neron thought (or maybe hoped) it would because no other finishes would be provided. The tow would cost about $4500/tonne and would be delivered in one cubic metre bales containing about 800kgs tow. The swabs and dressings would have to be based on unfolded single layers of the spread tow.

Global Spunbonding

David Price of John Starr Inc provided a snapshot of Starr's “Spunbonded PP World Capacities and Manufacturing Economics” study with analysis by region and producing company and this time including data on fabric area in view of the basis weight reductions.

• Growth would be 6% over the 2003-2008 period, with a 2 million tonnes/annum rate being approached by the end of 2008.
• This would be equivalent to 80 billion m 2 of fabric.
• 2/3rds of the production would be in NA and EU.
• 2/3rds of the production would be for hygiene applications.
• 80% of the 2008 output would be on modern (i.e. Reicofil 3 or 4 or equivalent) lines.
• It seems to be easier for new entrants to install the latest machines than it is for established producers to modernise.
• 70 companies were making PP spunbond in 2007.
• In 2008 75% of production would come from the biggest 17 producers.

An update on the 2003 report on spunbond polyester was also available and covered the period to 2012:

• This is less competitive than PP Spunbond due to the absence of reliable turnkey machinery.
• Recycled post-consumer PET waste is being used to reduce the raw material costs.
• Global demand will increase by 80,000 by 2012 allowing new entrants to install additional capacity, mainly in the EU and the USA .
• Roofing will be main growth market with “Others” and Geotextiles following.

Asked why capacity needed upgrading so soon after installation, Mr Price said the increasing demand for volume, quality, lighter weights, and lower costs meant converters rapidly moved on to the latest technology. In the USA 3 new lines had been announced (First Quality, Avgol and PGI) and in the EU a 7.2m line was under construction.

Global Wipes Markets

Virginia Lee of Euromonitor International re-presented some of the data used by Irina Barbalova at the Outlook 2007 meeting but gave more emphasis on wipes markets:

• Personal care wipes continue steady growth reaching $4.7 bn in 2006. Household care wipes have stagnated at about $2.9 billion since 2004.
• Wet floor wipes, dry electrostatic wipes, toilet care wipes, window cleaning wipes and furniture polish wipes were all expected to decline further through 2011.
• P&G's share of PC wipes has fallen from 20 to 17.5% of the global market between 2001 and 2006. J&J, Beiersdorf and private label have gained. K-C also fell (15-13.5%)
• P&G maintained share in household wipes over the same period despite strong gains from private label (up from 4.5 to 9%) S C Johnson was the main loser.
• New products mentioned were Lion Corporations Powder Sheets, Kao Corporation's Bioré Cool sheets and Cleansing cotton, Neutrogena Illuminating Microderm cleansing pads, and Ted Gibson's Hair Sheet (to calm frizz, refresh and shine).

The trends to organic, natural, fair-trade etc were repeated here, and Wal-Mart were said to be demanding more environmentally friendly products without any increase in price.

In response to questions, Brazil , China and Turkey in that order will show the strongest wipes growth through 2011. One novelty was mentioned: biodegradable packaging which could be buried in the garden after use had seeds embedded in it so that plants would grow from the rubbish.

Where next for Profit Growth?

Pricie Hanna of John Starr Inc observed that the hygiene industry is big and growing but profits are being eroded by commoditisation. Products which deliver the following features at the lowest cost are necessary:

• Ultra-thinness with flexibility, comfort and total freedom from leakage, e.g.
• Improved SAPs, airlaid cores, and pulpless cores to get softer, non-boardy products.
• Anything which reduces shelf-space and transport costs. (P&G's Easy Ups with hot melt/SAP and their economy diaper with pulpless core for China were mentioned.)
• Aqua-dry™ ADL based on perforated film from Tredegar now in use at Tyco, First Quality and Paper Pak
• White-Cloud training pants with acetate core met the requirements but for cost and leakages related to SAP migration. Wal-Mart has now withdrawn this line.
• Body-conforming stretch products which maintain fit during activity e.g.
• Stretchable pants can be made smaller and sold at higher prices, but more elastic and adhesive are needed to make them.
• Adult underwear based on Pull-Ups™
• Reducing the size range for incontinence products by using wide stretch side panels.
• Cloth-like aesthetics and softness
• Now moving into the adult market and appearing on diapers in the developing world.
• Cotton-like facings for fem care (new dry-weave on Always®).
• “Good Nites Sleep Boxers” and “Sleep Shorts” for older bed-wetters.
• Skin-friendly
• Products which maximise air flow to skin – especially in adult inco. (e.g. Prevail™ protective underwear with silky soft backing and ventilated waist bands.
• “Superabsorbent F Fiber” topsheet by Kao which promotes high air flow.
• Odor prevention and absorbtion
• Buffers in pulp and SAP to inhibit ammonia formation
• Easy to use and dispose of.
• Convertible diapers and diapers for standing changes.
• Wetter topsheets to assist potty training
• Environmentally friendly products in the UK and Australia : 70% biodegradable diapers ( Naty AB ?, and BioBaby from Mabe)

Innovation is now occurring further back in the supply chain and there are difficulties tuning this to market needs. Allocation of profit through the chain is biased to the retail end. Raw materials suppliers need to negotiate better deals and better sharing of IP. The need for nonwovens producers to reinvest regularly is a major challenge. Failure to do so attracts new entrants who further drive down prices.

Wal-Mart's focus on more environmentally friendly products at no extra cost is currently targeting other categories so the diaper industry has time to figure out how to respond to this coming need. The risk of new taxes on disposables is real.

The consumer now thinks products are thin enough and looks for improvements in the other areas listed above.

Olefin Block Copolymer Elastomers

Andy Chang of the Dow Chemical Co. described how their Insite™ technology platform using a breakthrough catalyst was allowing the development of the ethylene-octene elastomers in the Infuse™ range of polymers. OBC's use the same raw materials as random copolymers but arrange them into hard and soft blocks to give improved heat resistance and elastic properties. This arises from the crystal-amorphous granular molecular structure and manifests itself as a 50-60 o C elevation of melting point compared with the same monomers polymerised randomly.

Compared with the random version, OBC's show high retraction forces from a given strain, and if the density (crystallisation) is further increased the stress required for a given strain is doubled. Considering the levels of permanent set that can be achieved, OBC's can be seen to fill the performance gap between randomly polymerised olefins and the Styrenic Block Copolymers. Once stretched by 50%, the OBC's maintain a higher retraction force for a longer time at body temperature than other systems used in diaper tabs.

Asked about the price of the new polymers, Dr Chang said they would be competitive with SBC's.

Phase Change Materials in Rayon

Dr Stefan Sulzmaier of Kelheim Fibres GmbH ( Germany ) reported a successful project with Outlast Technologies Inc. on developing a microencapsulation polymer which would survive injection into viscose and the subsequent spinning washing and drying processes. The microcapsules (“thermocules”) appeared to range in size from submicron to 5 micron in diameter, and were being spun into a regular rayon fibre of about 3 denier, presumably without use of jet filtration. Outlast®-containing Danufil® rayon is now being offered for use in textiles and nonwovens. The microencapsulated Phase Change Material melts at 37 0 C, the latent heat of fusion/melting delaying the rate of temperature change of the fabrics containing it by absorbing or releasing heat. Fabrics containing it are selling into sports wear, especially underwear, and the one nonwoven application mentioned was golf-shoe insoles where tests showed lower sweat levels and greater comfort due to the PCM. It has also been incorporated into 100gsm air laid at MTS and into 60 gsm spunlace at Rieter. The fiber cost? Fibre can be bought at five times the price of regular rayon. How much PCM does the fibre contain? This was confidential.

Laser Cutting

Allesandro D'Andrea of Fameccanica Data SpA ( Italy ) introduced laser technology as a well established cutting method used in many sheet metal and piping industries and now being implemented on diaper and femcare production lines. The numerically controlled lasers don't touch the materials and never get blunt, and unlike water jet cutters, exert no pressure on the materials cut. Yet they are precise and fast moving in shaping diapers and pads and their use could make novel new shapes possible. However the energy used has to be precisely controlled to avoid burning the edges of the product (or the pulp core in the event of a malfunction), and there are some gaseous and powder emissions due to sublimation of the polymer.

Economic benefits arise on lines required to make 2 or more different shapes because the down-time for change over is negligible. 6 year ROI on a femcare line was put at 40% for 2 shapes and over 100% for 3 shapes. On a diaper line the figures were similar for ear cutting, but lower for leg cut-out (20% for 2 shapes and >100% for three shapes). Additional value was possible from reducing the time to market for new shapes, 2 days being claimed for laser cutting against 8-16 weeks for new rotary die-cut shapes. Finally, Mr D'Andrea thought the new system was an important step on the road to allowing his customers to realise their dream: hygiene product manufacture in a closed box without any human intervention. In response to questions:

• Two beams are needed, one for each edge.
• They will run tests on customers materials
• Basis weights up to 100 gsm appear OK.
• The molten edge hardness is acceptable according to consumer evaluations.
• No special containment is required for the sublimation products.
• Energy requirements were comparable to rotary and water jet systems.
• The system could be used for edge trimming of roll goods, but would only be attractive if (say) wavy edges were required.
• Lasers may be able to weld layers together as well (under development?)

Silicone Surface Modifiers

Mabrouk Ouederni of Wacker Chemical Corp described how silicones could be used to modify the hand and water sensitivity of spunbond, carded or air-laid nonwovens. They are by nature very hydrophobic and hence effective water repellent. Hydrogen methyl polysiloxane , cheaper than fluorochemicals, can be cured onto a fibre or fabric to give a permanent film, and this film can also be elastomeric and improve the elastic recovery of the fabric. It works on PP spunbond. At the other end of the scale, silicone glycols created by ethylene or propylene oxide modification of silicone are excellent wetting agents and combinations can tune the hydrophilicity to any desired level. Amino functional silicones give a softer more lubricious handle to fabrics albeit at the risk of some yellowing on prolonged storage. Silicones can also be used as melt additives and tend to migrate to the fibre surface after spinning. The nano-emulsions (<80nm) can be applied topically and soak into the polymer surface, softening the fibres, whereas the macro emulsions stay on the surface. In response to questions:

• Melt modification requires from 0.2 to 2% additions to the masterbatch.
• 0.5% of thermoplastic silicone elastomer can be matched to a PP spunbond to improve its elasticity.
• 0.3 to 0.8% is required as a fiber finish.
• The hydrophilic silicones will increase the wettability of cotton
• Using silicones on bico fibers could interfere with the bonding properties
• If silicone glycols are added for hydrophilicity, other materials might be needed to get the cohesion right for carding.
• The products are generally environmentally friendly and FDA approved – but not for all possible functional group additions.
• There have been no skin health issues.

Innovation in Air Lay

John Gearhart of Carolina NW Corporation described their narrow air lay line, recently installed to make high-loft waddings from natural materials, the displacement of glass fibre from composites and insulation being one of the main objectives. The line makes 300-3000 gsm waddings using 0.75 to 3 inch fibres with deniers of 1 to 400, at up to 20 m/min, producing 2500 kgs/hr of product. “Webs” up to 12” thick can be handled into the through air thermal bonder, but they generally consolidate to 9” thick on exit. They are supported through the oven by scrims above and below and if necessary films can be laminated to the bonded web at the exit. Fibres used include jute, kenaf, bamboo, coconut, cotton, wool, rayon, PP, PLA, bicomponents and PET, the thermoplastics being the bonding fibres. Recycled fabrics (shoddy) can also be used.

Applications to date include natural insulation (replacing foam or fibreglass) for green building projects, carpet backing, carpet tiles, filters, cotton absorbents, emergency blankets, agricultural and landscape fabrics, geotextiles, floor scrubbers, polishers and grinders. Powders could be added, but FR options had yet to be explored. Asked how the oven managed to get the heat through such heavy materials, Mr Gearhart said it was very special and alternated up and down-draught zones. Dust in the oven was not an issue, but had to be dealt with in the opening and blending areas which used standard off-the-shelf equipment – clothed with pins rather than wire. Bamboo was very popular currently (but from his description of the fibre he was talking about rayon made from bamboo pulp Ed.)

Elastic Spun Melt Nonwovens

Greg Ward of Phoenix Group (USA) described their patented (USP 6746978 etc) method for converting regular PP spunmelts (and other thermally bonded nonwovens) into elastic fabrics in an off-line stretching and heat treating process. The resultant webs are also softer and tougher than the precursor webs. Elastic properties were illustrated with the following figures for recovery within 10 seconds after a 50% extension:

• 18 gsm PP Spunbond 91%
• 100 gsm PP spunbond 88%
• 60gsm PP Meltblown 90%
• 24gsm PET spunbond 93%
• 70/30 PP/Rayon card-thermal bond blend 86%

The stretching and heat setting process reduced the width to about two-thirds of its original value. Extensions of up to 150% in the CD were possible after treatment.

Head covers and face-masks for use in surgery were demonstrated. In response to questions the new material had been used for stretch ears in diaper construction and Mr Ward thought it could be used for fully stretchable diapers. Surprisingly the barrier properties, loft and porosity all increase during processing. The cost was simply the cost of the nonwoven plus the costs of stretching and heat setting.

Ecological Wet-Wipes

Henri Laetervo of Suominen Nonwovens Ltd ( Finland ) observed that green consumerism was now a self-generating topic fuelled by attention seeking politicians and the media's linking of any odd weather event to global warming. It was in fact “media sexy” and had caught the imagination of modern youth who could adopt the cause safe in the knowledge that they were blaming the older generation for spoiling things. It had become mainstream and no longer the preserve of activists and the green movement.

Consumers were spending on goods which are most important to them and saving on the least important, but there was no real consensus as to what was important. They were prepared to do something easy for the environment on the basis that small things count, but would not yet jeopardise performance or convenience to be green. On this basis we need to think about life cycle analysis in laymans terms and address the need to:

• Increase Renewable materials usage
• Use certified materials according to whatever national standards apply
• Use organic materials where possible
• Use processes with improved energy, waste and emissions sustainability and processes which use fewer chemicals.
• Reduce transportation distance.
• Reduce multi-processed materials like rayon. (“why not use wool”!)

With regard to wipes production he advocated closing up the water systems of hydroentanglement processes to the standards common in the paper industry, and avoiding drying the nonwoven if the final application was a wet-wipe. In addition to replacing rayon with wool he suggested fibres could be extracted from sugar cane processing for use in nonwovens.

PGI's Spinlace™

Bob Dale of PGI (USA) initially provided INDA and PGI estimates of the North American wipes market along with miscellaneous data on spunlacing:

• Consumer wipes worth $3 billion at retail in 2006, used 2.3 billion m 2 of roll goods worth $425million. CAGR to 2011 would be in the 5-8% range. 61% of this value came from baby wipes, 25% from household wipes and 14% from other personal care wipes.
• Industrial wipes worth $922 million at manufacturing level in 2006 used 875 million m 2 of nonwoven, and would grow at CAGR of 5-7% through 2011. 50% of these were general purpose wipes, 22% were healthcare, 16% were foodservice and 12% were specialities.
• 435,000 tonnes of spunlaced nonwovens were produced, 193,000 in Europe, 128,000 in NA, 50,000 in China and 64,000 elsewhere. Wipes uses 40% of this tonnage, and have grown at 13%/year since 1990.
• Embossed spunlace is now used in most branded wipes and in 30% of private label.
• Spunlace capacity now exceeds demand so prices are falling while raw material prices are rising.
• Spunlace succeeded by cannibalising the pulp-based wipes so a reversion to pulp use is probably not the answer to rising costs.
• Raw materials now account for 60% of roll goods cost, and new high-speed wide machines are not the answer.

Clearly a breakthrough is needed and PGI think they have one in the shape of using their (old?) spun-laid lines instead of carding for most of the nonwoven construction, and using their Apex® patterning technology to add value. If more bells and whistles were needed, they could throw in a bit of pulp, make shaped fibres, add colors, use elastic or renewable polymers, and use a variety of finishing techniques. Asked if he had any samples to show, Mr Dale admitted that he hadn't.

Products of convenience

Jim Robinson of Mondi Packaging (Austri) reviewed the Latin American market for hygiene disposables with special reference to fem care products and his company's major offering in the sector, release paper.

• The global market for release paper for fem care is 1250 million m 2 , 40% of which is used in Asia, 28% in EU, 20% in the USA and 12% in Latin America .
• The world's top four fem care producers were P&G, K-C, J&J and SCA.
• Calculated per capita consumption of 2m 2 equated to 63 pantyliners, 48 napkins or 35 napkins with wings – for every man, woman and child in the world!
• Latin American consumption on the same basis would be equivalent to 14.4 trillion napkins.
• Ranked by per capita income in 2005, the top 5 LA countries were Mexico ($7310), Chile , Venezuela , Argentina , and Brazil ($3460) compared with $43,740 in the USA .
• Latin and Central American consumption of femcare products should grow at 4.1% pa through 2012 (J.Starr & GIA credited for this and the following statistics). Mexico would lead with 4.7% growth.
• Pads are much more acceptable than tampons. They are perceived as a necessity and their use does not vary greatly over the social scale. Product quality however varies greatly, with low earners buying cheaper and fewer products.
• Teen users are being targeted by the brand leaders, directly via teen websites.
• Private label is growing.

The challenges of the LA market for femcare materials were listed as rising manufacturing costs (especially energy and pulp costs), low economic growth in most LA countries, increasing import penetration, and increasing demand for sustainability from the major supermarkets. To address these issues, Mondi Packaging has invented a new pouch which replaces the backside release liner on a pad, thereby reducing raw material usage and cost. They are also trying to incorporate more natural, renewable, even dispersible and flushable biodegradable materials. In response to questions, Mr Robinson said shipping to LA added 12% and import duties a further 12% .

Where are the inventions?

Rick Jezzi (Consultant – USA ) observed that patenting activity is no longer an indication of innovation. Companies now patent what they are working on and no applications are rejected although some might be shortened. Most nonwoven technology used today was developed in the last century:

• 60's – “Chemical Era”: Dupont developed PP and PET spunbonding, PE flash spinning and spunlacing. Exxon developed melt-blowing, Monsanto developed nylon spunbond.
• 60's and 70's – “Spunmelt Era” : Lurgi & K-C commercialised the first “independent” spunbond process for diapers absorbents and wipes (“Coformed” with pulp)
• 70's – “Paper Era”: Air-laid developed as dry papermaking, was used in wipes and absorbents, and then stagnated for 25 years.
• 80's & 90's – “Film Era”: Apertured, breathable, elastic films

What next?

• Nanofiber production needs to be taken up by the nonwoven producers and developed into a viable route to ultra-light nonwovens from polymer melts.
• Innovation must be stimulated. Files should be mined to uncover the many good ideas overlooked in the last 30 years.
• Existing technologies can be combined to create new products.
• Spunbond speeds are still well below papermaking speeds. They can be increased further.
• Sustainability, biodegradability, flushability will all take hold and new products will need to be developed. (Dow's PE from sugar, and P&G's PHA's sold to Meridien were mentioned)
• Further opportunities for textile substitution.
• “Hybrid Technologies”: consider Reicofil 1 and 2 assets which are no longer economic for diaper components as part of new systems to develop new products.

Self Sterilising Nonwovens

Stephen Michielsen of NC State University described nylon nonwovens which can be activated by light to kill 99.9% of influenza viruses in less than 1 hour. Nylon spunbonds are coated with >0.1% a proprietary mix of binders and photoactive agents. All the active substances remain on the surface. When challenged with a broth containing 10 5 virus particles per ml, and then illuminated by a 5000 lux lamp for 1 hour, various levels of inactivation of the virus were obtained depending on the color of the fabric. Purple and yellow coatings were best with 99.99% virus inactivation. An untreated control gave 20% inactivated. Based on these results, Prof Michielsen expects an adequate 99% inactivation level to be achieved in either short exposure (~6 mins) or in much dimmer illumination. Uses in hospital products, masks for the general public and in animal husbandry were predicted. Attempts to coat polyester and polypropylene are in progress.

The Truman Nanoscope

Eric Rowley and Stanley Truman of TB Optics updated last year's paper on the use of a light microscope with light staining techniques (prisms to filter out all but a narrow band of wavelengths) to view “live” uncoated samples in ways not possible using the more costly SEM techniques. This year they have added a Rotary Monochromatic Dispersion Unit which allows the mechanical selection of a wavelength band. Portions of the sample fluoresce as the resonant frequencies of their chemical components are reached. Colloids, living cells and nanofibers have been studied. Relevance to nonwovens seemed contrived.

Pulp Defibration

Mark Bolyen of MTS provided another comprehensive review of how different hammermills on different settings with different pulps have, over the years, given absorbent pads with different performance characteristics. The conclusion? The hammermills need setting up carefully and optimising for each pulp and when this is done any of the pulps can give top performance. Mr Bolyen thought differences in performance were not great, and admitted defibration issues had largely disappeared since the pulp producers had improved their products.

Ya Gotta Wanna

Andrew Urban (Consultant) related his experiences in process control from 40 years in the nonwovens converting industry. The conclusion? Keeping nonwovens conversion under good control paid dividends in extra production (up from 10,000 to 14,000 diapers per hour), reduced waste (4.5% down to 3.5%) and reduced labour (5.5 down to 3.5 per diaper line). The costs of implementing process control? About $250,000 over 3 years on 13 lines in 5 diaper plants, apparently at Pope and Talbot.

Calvin Woodings