Wednesday, 2 May 2001

Nonwovens Technology Conference Mainz : April 24-26th 2001

Mainz Hilton Hotel

Despite being scheduled simultaneously with the Tech-Textil 2001 Exhibition and Conference in neighbouring Frankfurt, this Marketing Technology Services meeting attracted 140 international delegates. As in past meetings in this series, strategy and air-lay technology themes predominated, but papers from both Perfojet and Fleissner heralded some new thinking in hydroentanglement bonding.

Key Points

  • Main Spa ( Italy) is starting a new flexible air-lay line and is prepared to run trials with lyocell.
  • Rieter-Perfojet has installed the first HE bonding head on a spunlaid line, apparently to entangle pulp into the spunbond for wiping applications.
  • Fleissner is oscillating the last HE nozzle to make fabrics free of jet lines.
  • Both HE machine makers are focussing on efficiency and economy rather than the extremes of pressure and width.
  • A pulp-free diaper made from 2-layers of film with SAP in channels, said to be able to deal equally well with thin and thick fluids is to be commercialised.
  • Superabsorbent-containing soaker pads for meat & fish retail packs can be air-laid and converted on panty liner machines.
  • An 11gsm spunbond coverstock can be made with the same strength and porosity as a 15 gsm product if 350 MFR resin is converted at high spinning speed.
  • Eastman’s EASTAR BIO® biodegradable co-polyester has been melt blown and spunlaid successfully.
  • 130,000 tonnes of pre-formed core is used in fem-hy and inco products. The first diaper to use the core is now on the market.
  • Data from K-C’s Kellenberger patent on AUL/Overnight leakage has been found wanting in an analysis by MTS.

    Air-Laid in Meal Service

    Johanna Svanberg of Duni AB said Duni has focussed on the meal service market since 1972 guided by a mission “to enhance any eating and drinking occasion”. Having introduced the first coloured napkin in 1954 they now produce a wide range of disposable table-wear including paper cups. Linen-like latex-bonded air-laid napery, often brightly coloured and printed is perhaps the best-known Duni product. The market, and hence their product development, is heavily influenced by clothing and interior design fashion, products changing twice a year to reflect trends in summer and winter season colours, textures and prints. Last year, Asian character prints were “in”, next summer the themes will be “Mirage, Innocence, Frivolity and Sensation”. Technically speaking:• Duni has a new air-lay forming head (Danweb) to complement the M&J systems they've used for years.
    • Most of their printing was flexographic.
    • They've developed biodegradable bonding systems, but there's no demand for them as yet. She commented that there were however spin-off benefits, but could not say more. (maybe easier waste recovery)
    • Cost reduction was as important as staying in fashion. The key was to make no waste – because bonded airlaid could not be re-fed – and to reduce energy use.
    • They used LPG for drying, but now the prices of this fuel were increasing so dryer exhaust heat recovery would be their next major project.
    • Environmental concerns surrounding disposables had to be addressed: their echo-profiling (sic) showed that air-laid table-wear was no different to laundered cotton for total environmental impact.
    • The European Community's Integrated Product Policy (Feb 2001) would stimulate a) a consumer demand for “green” products, b) a business leadership to develop green products and c) a price incentive to switch to green products.
    Why did European-style tablewear not do well in the USA ? Ms Svanberg thought it should be a big opportunity, but felt Duni still had to find the right distribution channels.

    Fibervisions Bico Fibres

    Allan Rasmussen of ES Fibervisions took us once more through the ES family of thermal bonding fibres now on offer. Along the way, the following points appeared more interesting than most:
    • A new polymer additive that is now used in the whole range of products has solved their problems with fibre yellowing on storage.
    • Their capacities for bico fibre are 12,000 tpy in Athens Georgia , 15,000 tpy in Varde Denmark , 10,000 tpy in China , and Chisso has 45,000 tpy in Japan of which 10,000 are available for export.
    • The AL Adhesion C product which bonds well to cellulose and cuts dust levels in airlaying uses a hydrophilic additive grafted into the skin polymer.
    • Their low-melt (95 o C) fibre gives very soft nonwovens with poor recovery from compression, but it can be used as a laminating layer or even a coverstock.
    • While they offer up to 20mm for air-lay, 6mm is the longest fibre used commercially.
    • The 17 segment splittable PP/PE bico (Chisso EDC) does not split in the air-layer.

    Honeycomb structures

    Ronald Smorada of Versacore (in another run through his IDEA 2001 slides & video) explained that his 3-D nonwovens process was a new application of the technology previously used to make paper, aluminium and Nomex honeycombs. Using nonwovens intermediate in properties between these low and high technology extremes could create new markets. He described the opportunity as a market development exercise in transportation, furniture, civil engineering and filtration sectors. If the machine worked at its optimum settings with 100mm wide, 100gsm tapes it would produce 0.5MMlbs, or 20,000 m 3 product per year. On-line slitting had been developed to allow the 100mm tapes to yield several layers of thinner honeycombs. Details of how the product would be packed for shipping were not provided, but with nonwovens, slabs of the honeycomb could be flattened and re-expanded at the destination. In response to questions, cost could be estimated by assuming 65% of the final cost would be the cost of 100gsm 100mm tapes. This worked out to $20-$85/m 3 , compared with $3000/m 3 for Nomex honeycomb. The process could be made to work on non-thermoplastics using adhesives, but this is regarded by Versacore as an unattractive niche market.

    An Alternative Air-laid Strategy

    Domenico Milesi of MAIN Spa estimated total air laid capacity to be ~350,000 tonnes currently and growing sufficiently fast to justify his investment in the technology. His strategy had been to:
    • Get some money
    • Decide what sort of factory to spend it on
    • Build the factory
    • During the 16-month construction process, work out where he was going to sell the product.
    • Hire staff, especially an excellent R&D team to develop new products.
    The key to succeeding with this delightfully quick and dirty approach was in his view to move into a fast growing market where the future was unpredictable (so why waste time trying), and to spend a little more on the kit so that the plant was versatile enough to be able to produce a wide range of products. His 10,000 tpy Dan-Web line had four forming heads followed by foam application of latex from both sides. Each head could take 2 different man-made fibres and 2 different pulps, and he could add SAP between heads 2&3 and/or 3&4. 576 different combinations of raw materials are theoretically possible. Having completed construction last June, he was now developing products to customers specifications and had already identified a newish sector suited to the output: soft-fruit packaging. In Italy alone, the potential here, at 20-25,000 tonnes/year was more than enough to take his entire output. From his base at the instep of Italy , he saw the possibility to ship into France , Greece and Turkey as well. Asked about air-laid diaper cores, he thought their production was very close now.
    Klaus Völker of Rieter-Perfojet described the strategy changes since the Rieter takeover. “Jetlace 2000” had been a rather short-sighted designation for a process developed at the end of the 1990's so they were renaming it “Jetlace 3000”. The name change also heralded a new direction which would value efficiency and economy over ever-wider ever-higher-pressure systems. Higher water pressure hit investment and energy costs, both doubling for every 100 bar increase in pressure (above 100bar). At 100 bar there were ways to use water more efficiently, e.g. perforated flat-screens rather than woven wire belts to support the web. With these screens, there was a trade off between bounce-back and flooding, but tests had shown that only 8% open area gave sufficient drainage and much enhanced fabric strength. Fluid dynamics studies had allowed changes in the design of the injector strips and water distribution channels to allow products previously requiring 300bar water to be made with only 180 bar. In addition to these efficiency changes, the cost of an HE bonding zone was now 30-40% lower than 10 years ago. Other points of interest:
    • Fabric strength was unaffected by line speed up to 100 m/min, but above that pressure increases were needed to maintain a given strength level.
    • The highest commercial line speed was currently 230m/min (4meters wide with a 17,000 tpy output).
    • The Airlace system was illustrated with an HE zone either side of the M&J air-layer, but it was also possible to sandwich the pulp between two card webs. In this case wet-waste levels were horrendous (10 tonnes/day had to be dealt with).
    • Pre-entangling the card web before laying the pulp allowed the pulp to bond better in the second HE zone because it washed into the corrugated surface (jet lines).
    • They sold their first HE head for use on spun-laid last year, mentioning a spun-laid/airlay pulp/HE system for wipes.
    • Smaller holes give more efficient entanglement – now using less than 100 micron.
    • Cavitation problems were significant above 300 bar, but manifold design had helped.
    • Demineralised water was more aggressive than ordinary! (Jet strip life reduced by faster erosion)
    • All finish was removed from fibres by HE so PP emerged hydrophobic. Defoamers had to be added to neutralise the finish in the water system.
    • Jet strip cleaning frequency had improved from once/shift to once/week with the new filter systems.

    Fibre-Free diapers?

    Harry Boich (Consultant ex Corovin) has developed, patented and obtained finance to commercialise a “body hygiene liquid management system”. He argues that fibres are poor transporters of liquid because of the difficulty in getting the capillarity effects right. He goes on to say that absorbtion and transport, both needed in a diaper cannot be achieved with a fibre structure, and that fibrous cores and topsheets cannot be made to deal equally well with thin and thick fluids. His patented solution is to use films with tapered channels to conduct fluid away from the crotch area and into foam/SAP reservoirs in the waistband area. From the unhelpful slides it appeared that alternate channels contained SAP, the empty channels being designed to maximise capilliarity. It was not clear how his claim that the product would work equally well with thin and thick fluids could be justified. Lab test data is said to be excellent, but consumer testing has not yet been carried out.

    Market Update

    Johns Starr reviewed industry competitiveness in the light of increasing raw materials prices and new capacity coming on stream.
    • He saw brief overcapacity in spun-melt nonwovens for hygiene, with new lines full and older lines underutilised.
    • Global demand would reach about 1.1million tonnes in 2005, and some older lines would have to close if they could not move higher value products. (Retrofitting of microdenier/bico capability?)
    • Apart from some overcapacity in Miratec at PGI, he saw spun-lace in balance with demand reaching 250,000 tonnes by 2003. (he uses best estimates of the most likely output of the lines to get the capacity figure, ignoring the manufacturers nameplate capacity.)
    • Full-cost of all-staple European spun-laced from the most efficient lines would be around DM8/kg, raw materials accounting for half of this.
    • Materials and fixed costs for airlaid core at 500 gsm would about $1/m 2 with 90% of this being materials.
    • Full cost of needled polyester would be around $2/m 2 with materials amounting to $1.1/m 2 , but no basis weight was provided.
    In response to questions:
    • PET spunbond would grow more slowly than PP, but had good prospects in filters, automotive, roofing and construction. (The recent start-up and close down of a new US line was a hiccup).
    • Carded/thermal coverstock has about 20-40% of the market and will decline further.
    • Carded/latex-bonded ADL was still in use thanks to new investment in high capacity lines.

    Nanofibres Update

    Michael Wehmann of Nordson Fiber Systems presented selected slides from several earlier presentations on microfibre production.
    • JM1 meltblowns had a 1.5 micron mean fibre size: JM2 had a 1.1mmfs with a standard deviation of 0.464
    • Finer fibre production needs better quality polymers.
    • Moving to 800MFR PP gave a fourfold improvement in productivity when spinning 3 micron fibre.
    • Meltblowing splittable fibres and then hydroentangling could make “Nano” fibres them.
    • Islands-in-a-sea (900 islands) could be meltblown and split to give fibres in the 100 to 800 nanometer diameter range.
    • Electrostatic spinning could give 0.05 micron diameters.
    • “Spin coating” appeared to be electrostatically-assisted centrifugal spinning involving a membrane as the spinnerette.
    • A second slide with the same “spin coating” title referred to the University of Texas (Dr. Paul) production of carbon nanotubes a few atoms wide as “soot” from vaporising graphite electrodes in a helium atmosphere.
    • Dr Ghosh at NCSU has improved filtration by adding 5% of electrospun nano-fibres to meltblown.
    • Nordson had co-form experience (they could blow pulp into the melt-blown.
    • Die holes were now 0.3 to 0.4 microns for 3-5micron fibres. 0.1mm holes could be made with lasers..

    Superabsorbent Soaker Pads

    Scott Tomlin of Stockhausen described how superabsorbents could now be used in soaker pads under pre-packaged meat and fish portions. 13.5 billion of these were used annually in the USA , and could use 40,000 tonnes of airlaid nonwoven if each pad contained 1 gm of SAP. 60-70% of the pads were used for red-meat. The US market was thought to be worth from $75MM to $120MM. Compared with the commonly used tissue/film pads, Favor-Pac® SAP/air-laid pulp contained in a sealed perforated film pouch had many advantages:
    • Better protection against leaks.
    • Better, more hygienic appearance.
    • Higher perceived food value.
    • Lower repacking costs at the retailer.
    • Fluids which could be contaminated with salmonella etc could be immobilised and disposed of more safely.
    Compared with a SAP-free control pad, the addition of 0.75g of Favor-Pac® doubled the absorbency and increased the retention of fluid 8-fold. Absorbency under a typical chicken load was increased from 57 to 92 gms and the fluid remaining in the tray when discarded was down from 42 to 7 gms. Safety issues had been dealt with in the USA by getting FDA approval for Favor-Pac® for indirect food contact 2 years ago. In Europe testing at TNO was establishing conformance to the limits for global migration of monomers. Monomer levels would have to be declared, and continuous monitoring of pad production would be needed. Some problems:
    • Dosing of 0.75gms of SAP was too variable.
    • Getting older, low productivity machines set up to handle SAP was costly.
    • Overall cost of the new pads is hard to justify for retailers.
    However Mr Tomlin was confident that the problems would be solved, and that the soaker market was similar to the diaper market when diapers used 55gms of pulp.
    It would probably be easier to adapt a panty-liner machine to make the new soakers than it was to retro-fit SAP handling to the soaker pad process.

    A new HE Strategy - Part 2

    Jürgen Heller of Fleissner continued the theme set by Rieter-Perfojet and emphasised the potential economy of HE bonding. He put 1999 actual production at 230,000 tonnes, about twice the level reached in 1995 with growth expected to continue. 60c/lb fibre could be converted into roll goods with a value of $2.7/lb and there was still room for efficiency increases. For disposables, energy costs were only around 1% of the roll goods cost. On the basis of a 3.5m line working at 100m/min for 7200 hours/year to make 60gsm nonwoven, a 1% increase in efficiency would give $600,000 per year more revenue, and in many plants an increase of 10% in efficiency ought to be achievable. Lower pressures, in addition to the direct savings of energy would allow jet strip life to be increased dramatically (“from days at high pressure to months at medium pressure”). Jet cleaning interval could be extended to weekly or even fortnightly by tighter filtration. One innovation appeared: an oscillating last nozzle to kill jet lines. The vibration had to be low amplitude and high frequency to be effective. Illustrations of 3D water-marking effects achieved by using patterned drums were shown. Drying energy? About 1 KwH per kg of water going into the dryer, and for PES they achieved 1 kg water per kg fibre at the dryer inlet. For viscose the figure was 1.3 kgs water/kg fibre. Had they tried denser fluids than water to get more energy transfer? No.
    Spunlace strength v. energy input

    A new Spun-Laid Strategy?

    Anders Moller of Ason engineering made a case for spunbond producers to emulate the tissue paper industry rather than the newsprint sector. He thought very big inflexible machines were wrong for a rapidly changing nonwovens industry and thought the way forward involved:
    • Smaller machines closer to the markets.
    • Machines capable of running any fibre-forming polymer with minimal change-over time.
    • Machines capable of making bico fibres with no capacity penalty.
    • High spinning speeds to allow a) economic production of sub-denier fibres or b) higher throughput per metre width, and/or c) much stronger filaments.
    • Higher hole-density in the jets (productivity/metre)
    • Removing the need for SMS by achieving the same average denier in direct high speed spinning of strong continuous filaments.
    • Using high MFR polymers, which worked well at speeds above 4500m/min. For instance 700 MFR PP could be spun to 0.2 denier/fil at 6,000 m/min.
    • Targeting textile markets (like Freudenberg with Evolon®)
    Such processes would allow the basis weight of coverstock to be reduced while maintaining cover and tensile strength. (11 gsm PP made from 350 MFR resin at high speed gives the same hydrostatic head as 15gsm made from 35 MFR.). Trials with Eastar Bio™ copolyester on Ason equipment in the last month have revealed excellent spinnability at speeds above 4500m/min to give 1 dpf fibres and fabrics from 17 to 120 gsm. The 105 o C melting point resin was spun at 205 o C and bonded at 80 o C. There was some evidence that the polymer degrades in sea-water also.
    Mr Moller thought electrostatic spinning was many years from commercial reality and would be difficult to operate above a kilo per hour per metre width. His process could make 0.4 denier fibre at 100kg/hr/m/beam.

    Inorganic Biocides

    Ken Code of Biolargo Technologies Inc., a start-up company about to go public on the NASDAQ exchange, saw the possibility of making air-laid nonwovens the carriers for a powerful disinfectant which would allow “Universal Precautions” to achieve portability in the form of pads and wipers, bandages, disposable clothing, food and hospital service nonwovens and packaging for dangerous liquids. Precisely how this would be done was a little unclear, but the following points were gleaned:
    • Iodine would be used at levels below its water solubility limit (337ppm) to provide a cheap but intense kill rate. (log 6 in 5 minutes quoted).
    • Copper was involved to give a background (log 3) kill over extended periods to maintain “sterility” after the iodine release.
    • These inorganics would be carried in a SAP. (Stockhausen's Favor Pak 100 mentioned as being dosed with 5 to 400 ppm of the active ingredients.)
    • Some interference was noted: SAP swelling was reduced by the polyvalent metal ions, and the efficacy of the antimicrobial was reduced by the swelling of the SAP.
    • The immediate target market for the airlaid was packaging for the 5 billion Vacuutainer tubes sold by Becton-Dixon to transport samples of body fluids. Here several aspects of “universal precautions”, i.e containment (of spillage), isolation, neutralisation and disposal, were dealt with at the same time as providing a cushion against breakage.
    In response to questions Mr Code said that the iodine concentration was too low to cause either the skin irritation or the staining familiar to those who used the early disinfectant. “Copper kills by acid hydrolysis”. The SAP loaded with Cu and I 2 is being converted into airlaid by Concert in Canada . Polycarbonate plastics, like copper, are “natural killers” of bacteria.

    Cost effective diapers from pre-formed cores?

    Donald Young of Rayonier considered the difficulties of getting a diaper maker to choose pre-formed cores over making his own. Fem-Hy makers and inco-pad makers had made the switch, and the use of airlaid cores were growing nicely in these sectors, but so far only one diaper maker has put a product with a pre-formed core on the market. Fem-Hy and Inco sectors account for about 680,000 tonnes of core materials each, the former using 110,000 tonnes of pre-formed C-fold core, the latter 27,000 tonnes. Diapers, with 2.9 million tonnes of core and “zero” pre-formed are clearly the big target. Cost was the key, and because diaper producers wanted pre-formed core to have the same cost-performance as regular cores, the target price for pre-formed could be calculated as $34.75/thousand diapers. The best achievable with pre-forming was now $39.21/thousand. One solution proposed by Mr Young was to try to persuade diaper makers to look at the total system cost, not just the core costs. If waste, packaging, transport and conversion costs were included, savings in these non-material items allowed pre-formed and conventional diapers to reach the retailers shelves at the same total cost – said to be $55.60/thousand. He saw further benefits arising from the fact that the preformed cores could be made lighter than conventional cores. His air-laid capacity slide gave 348,000 tonnes as the current global figure, with 450,000 tonnes expected by the end of 2002. P&G's air-laid capacity was put at 24,000 tonnes and McAirlaid's nominal 40,000 was actually 20,000 tonnes. Mr Young's paper was not in the proceedings.

    Durable biocides

    Claudio Darpin of Sanitized AG reviewed the need for antimicrobial additives and the factors to be considered in choosing the right type for a given nonwoven or fibre.
    • Natural and cellulosic products were best treated by padding or spraying the organic biocides either directly or in a binder. Wash-fastness for the life of even a durable textile was achievable on these fibres by this method.
    • For thermoplastic synthetics several approaches are possible, but the inclusion of the agent in the polymer via a masterbatch worked well in most cases.
    • Active organic additives were suitable for the lower melting PP and PE fibres. (E.g. Sanitized® MB P 96-60 at 2.5% in PP)
    • Inorganic additives were needed for PES and PA (melting points above 250 o C) and silver based products were favoured. (E.g. Santized® Silver, where the silver was in a white ceramic carrier)
    The silver product conferred antimicrobial activity for 7-10 years, and a new material with a 15 year guarantee was now under development. A wash-fastness of 100 cycles using a standard ISO 95 o C wash with bleaching chemicals could be achieved. Mr Darpin agreed that the materials were over-designed for disposables use. The chemistry of the organic Sanitized? It was a heterocyclic substance.

    Air-laid Throughput increases

    Jim Westphal of Troika Nonwovens (formerly with Merfin and Buckeye) was now representing Dan-Web A/s to give a paper on improving the throughput of air-laying with drum formers. The trials had involved treated and untreated pulps alone and in blend with both 4mm and 6mm bicomponent fibres at 10, 20 and 30%. 100gsm webs were made using 37mm 2 slots in the forming drums with 100% and 125% forming air velocities.
    • The treated pulps gave substantially higher throughput than untreated, in some cases nearly doubling the capacity of the former.
    • Increasing air velocity by 25% gave a small (8%-10% i.e. uneconomic) improvement in capacity.
    • Adding 4mm fibres to treated pulps did not affect the throughput, but 6mm fibres reduced the capacity; 1.7 dtex having a greater effect than 3 dtex. The losses ranged from 6 - 24% for a 10% blend to 39-46% for a 30% blend.
    • Adding 4mm fibres to untreated pulps increased the throughput by 7.5% at a 10% addition of the bico fibre and by 40% for a 30% addition. 6mm PP-cored fibre additions caused a small deterioration in throughput with this pulp, while 6mm PES-cored fibre gave a slight increase of capacity.
    • Higher capacities were obtained when blending 4mm fibres with untreated pulps than by blending 6mm fibres with treated pulps.
    Throughputs ranged from a low of 130 kgs/hr/metre (untreated pulp, with 30% of 6mm fibre) to a high of 330kgs/hr/metre (treated pulp with 20% of 4mm fibre) indicating the profound effect of the variables studied. Further work is planned.

    Meltblowing Biodegradables

    Prof. Dieter Müller of Bremen University re-presented his INTC 2000 paper on melt-blowing biodegradable polymers and extended it to consider applications of PEA and PLA in more detail. Polylactic acid, polyesteramide, polyvinyl alcohol, cellulose diacetate and a polycaprolactam/thermoplastic starch alloy were all meltblown on the 1” extruder at Tandec. Polypropylene was the control. Only PLA and PEA (after adding 3% glycerol) gave fibrous webs like PP, but only PEA gave a nonwoven with usable strength. (PP meltblown was 40 times as strong and 5 times as extensible as the PLA, but only twice as strong and only one fifth as extensible as the PEA.) Neither PVOH, PC/TS nor cellulose diacetate, even with 10% glycerol added, would form fibres. The chart of polymer prices showed PP=0.45, PEA=1.3, PLA=0.75, CA=1.55, and PCL=1.75 and TPS=0.6 c/lb. Prof Müller considered the key properties of PEA to be:
    • High strength and extension
    • High stiffness cf PP or PS
    • High “form constancy” against thermal impact in the 100-140 o C range (ISO 75).
    • High impact strength at low temperatures (-30 o C)
    • Food contact approval. The polymer is already used in disposable cutlery.
    • Conforms to DIN 54900 biodegradability standards.
    For comparison, PLA showed:
    • High resistance against grease.
    • Can be modified to be flexible or stiff.
    • Food contact approved.
    • Industrially compostable according to ASTM D 5338, but not suitable for home composting.
    • Melts between 120 and 170 o C, but a softening point of 55 o C according to EN ISO 306 may be limiting.
    In response to questions he revealed that PEA was no longer in commercial production, the only supplier, Bayer ( Leverkusen ), having decided to close the plant as uneconomic in the last few weeks. Bayer were however looking for possible purchasers of the technology. Asked about Eastmans Eastar Bio® biodegradable polymer, he said that also in the last few weeks, samples had been meltblown at Tandec. They were similar to PEA in character showing good processability to give even fabrics with good strength and elasticity. Biodegradation was good and there was some evidence that it disappeared in seawater also.

    AUL and K-C

    Mark Bolyen of MTS pointed out the short-comings of the absorbency under load test with particular reference to K-C's claim in USP 5147343 that high AUL surprisingly correlated with reduced overnight leakage of diapers. This had been accepted as a valid claim and referenced in #5601542. Mr Bolyen pointed out that AUL was probably OK for SAP QC work but there was no evidence that AUL correlated with diaper performance in use:
    • There was no way to pressurise the insult area of a diaper in use.
    • Why 3psi? It was the pressure which showed the maximum difference between SAP's in Stan Kellenberger's 1992 patent (#5147343 for K-C).
    • Any test which allowed 1 hour to reach equilibrium was silly in the diaper performance context
    • The cylinder weight tended to stick in the cylinder cause massive AUL errors.
    • Seiving SAP prior to testing (to remove the dust that causes sticking?) does affect the results and is another undesirable procedure.
    • Testing polymer alone (vs in pads) was a dubious basis for claims on pad performance.
    • Reproducibility between labs testing the same SAP's was poor.
    • K-C's claim that weight of SAP used per diaper (3,5 or 7 gms) does not affect overnight leaks - but AUL does - is not borne out by a re-analysis of the data in the patent.
    Was this academic? No. K-C were now effectively claiming that use of SAP's with AUL above about 25 in diapers was their invention, thereby restricting further SAP development. The patent is unlikely to be upheld in Europe but could be troublesome in the USA .
    Calvin Woodings 3/5/01