Thursday, 25 April 2002

INDEX 02: Geneva - 16-19th April 2002

  • Cargill Dow is keener to develop nonwoven applications for PLA now that the 140,000 tpa polymer plant is on stream.
  • Micrex has developed a version of its compressive shrinker to work on an HE line for wipes production.
  • JATI has shown conulated film to be an excellent subfacing on its Mega-Thin concept diaper.
  • Celli has developed a version of its leading slitter/winder with a Nordson hot melt spray laminator built in
  • Reicofil 4 spunbond lines target fibers down to 1 denier, fabrics down to 10gsm and throughput up to 50% higher than Reicofil 3.
  • Russian pure, soft flax appears more wettable and absorbent than rayon.
This was a smaller INDEX conference than usual with fewer papers and a disappointing number of originals.

No Guarantees – Only Opportunities

Karl-Michael Schumann of Procter and Gamble
Karl-Michael Schumann of Procter and Gamble introduced and chaired a series of short presentations under the title “Winning in the market place through technical and commercial innovation.” Between 1998 and 2002 the dollar value of P&G's nonwoven purchases had increased by 30% due to the introductions of successful new consumer products such as Olay® facial cleansing wipes, Thermocare® bandages, Bibsters® baby bibs and Swiffer Wet-Jet®. Further growth was clearly possible, but a new approach involved ever-closer collaborative work between P&G and its suppliers. The current development fashion for conservative, incremental improvements was essential, but would never drive substantial growth. Breakthrough developments involving disruptive technology which obsoletes current assets and requires massive capital would continue to lead to the growth of whole new industries, but these were essentially unplannable and uncontrollable. P&G felt that the nonwovens industry should target Conservative-Breakthrough developments capable of delivering a step-change in value without requiring massive capital.
A new licensing policy was now giving suppliers access to all P&G technology, examples being Nodax™, SAN and DEC:
Nodax™, a fully biodegradable and compostible polymer developed by Dr Noda of P&G Bioplastics from renewable resources. Dr Noda described the family of polyhydroxyalkanoates as semicrystalline, thermoplastic polyesters produced directly by bacteria. Benefits claimed were broadly the same as for Cargill-Dow's polylactic acid (PLA). Target price when fully commercial was put in the $1.50 - $2.00 range.
Kaneka in Japan has licensed the polyhydroxybutyrate-hexanoate version Nodax™ and Dr Masahiro Asada
presented its properties saying that PHB-H resembles polyolefins in properties whereas PLA resembles polystyrene. PHB-H appeared to have lower strength (about half PLA) this being accompanied by much higher elongation. Melting temperatures, around 170 o C for the pure PHB, fell to around 120 o C as 10% of the hexanoate co-monomer was introduced.
John Curro of P&G introduced the P&G Stretch Apertured Nonwoven (SAN) technology now licensed by BBA nonwovens. Dennis Tavernetti of BBA described BBA's involvement with P&G, and reported a great improvement in openness and rate of progress to new products. SAN technology allows several nonwovens to be combined in a line-bonding calender, and then laterally stretched so that the fused lines open up into apertures. This gives very clear holes with fused edges and hence a better looking, lint free product. BBA are now using it to make coverstock for newborn and nursing diapers.
John Curro
John Curro also introduced the related Differential Elongated Composite (DEC) technology in which a non-elastic fabric is sandwiched between two elastic fabrics prior to “ring-roll” stretching. Doug Small of Precision Fabrics Group described their use of this technology to make the Dryel® dry-clean bag for P&G, and their own Diamond Dry® absorbent pads used in food packaging. Both products featured a highly absorbent core, the Dryel® featuring controlled release, and Diamond Dry® featuring high retention under pressure.
In concluding , Karl-Michael Schumann called for further innovations in the following areas:
• Improving cost/performance.
• Adding functionality such as extreme hydrophilicity, extreme hydrophobicity or controlled pore size distribution.
• Improving aesthetics with new textures, sensory properties, colours and patterns.
• Using sustainable polymers.
Asked how much extra business would arise from all this R&D he said there were no guarantees, only opportunities.

PLA Update

Marcel Dartée said Cargill Dow LLC now employed 230 people and had spent a total of $750 million to develop polylactic acid to the point where the 140,000 tpa polymer plant in Blair Nebraska was coming on stream. The company is driven by the need to create sustainable products by eliminating the need for fossil resources and to deliver against the triple bottom line of economic, environmental and social targets.
The key attributes of fibre made from the polymer are:
• Wettability
• Low odour retention
• Does not support bacterial growth
• Transparent to (and hence unaffected by) UV.
• Compostable
• Flame retardant
• Resilient
• Stain resistant
• Soft and drapy handle
Marcel Dartee - PLA Biodegradation
In response to a question from Procter and Gamble, Mr Dartée provided information on where CDL expected to sell the 140,000 tonnes of polymer. It would be split between packaging (film and containers), chemical intermediates, and fibres (both filament and staple for both nonwovens and textiles). Would the plant make only one polymer type? Yes, the polymer based on L-lactic acid. They can add a little D-Lactic acid and will experiment with copolymers, but these would not be commercial in the near future. Asked about how the basic fibre properties compared with the main fibres:
• Tenacity was equal to polyester
• Abrasion was between that of polyester and nylon
• Exact pilling performance was yet to be established but was likely to be comparable to polyester.
• It was more elastic than polyester.
• It melted at lower temperatures and this could be used in thermal bonding.

Mega-thin Mark II

Reiko Moriya of JATI ( Japan ) provided further information on their “Mega thin” diaper concept. The new Liquid Distribution Unit appeared to be a vacuum perforated PE film, thicker and harder than the Always® topsheet and with bigger holes. This channelled and stabilised irregular flow to the core and encouraged more spreading and hence more complete use of the superabsorbent. The core comprised a 40gsm nonwoven with 180 gsm of superabsorbent powder printed onto it in lines. The new LDU was said to increase absorbency rate by a factor of 6 and to quadruple the area wetted. Retention over the range 0.1 to 0.5 psi was fairly constant.
Mega-thin core plus LDU gave 1 st to 3 rd insult times generally less than half that of commercial diapers. A 100 consumer panel test was said to have confirmed the superiority shown in laboratory evaluation.
Asked if the film used was commercially available, Dr Migaku Suzuki, replying on behalf of Ms Mori said it was, and was on display at this show.

More Permeable Superabsorbents

Dr Edgar Hermann of Hy-Tec Hygiene Technologies GmbH defined SAP permeability as the liquid flow through a pre-swollen gel. To improve permeability it was therefore necessary to make SAP particles that kept their shape when wet and under pressure. This, coupled with the fact that permeability implies spaces in a gel, means that permeable gels have lower absorbent capacity than non-permeable gels. To explore this interaction, Hy-Tec had studied 6 powders, each submitted by a separate producer as illustrating the best balance of permeability and capacity.
• Permeability Under Load varied from 21-63%. (PUL was defined as the ratio of AUL of a 5 gm pad of SAP to that of a 0.9gm pad of SAP: the latter assumed to be fully wettable without permeability coming into play.
• PUL does not correlate with P&G's “indicative only” Saline Flow Conductivity test for permeability.
• Time-dependent absorbency was similar for all.
• 4th Insult absorbency varied from 492 to 764 mls.
• Sample D gave the best overall ranking, but Dr Hermann could not reveal the identity of the SAP's
He concluded that products with high retention and permeability were now commercially available.
Steve Christensen of Dow's Drytech Superabsorbent Products division described ways of controlling the absorption rate of superabsorbents.
Faster absorbing (less permeable) SAP's could be made by increasing the surface to volume ratio either by creating wrinkled particles or by agglomerating fine powders into larger particles using glycerine or polyethylene imine. Agglomerates tend to either break up too easily in diaper making or if well bonded, give too low a capacity. Dow has a new binder that gives high attrition resistance and very fast uptake rate (11 secs on the Vortex test c.f. 80 secs for the control).
Slower absorbing (more permeable) SAP's can be made by reversing the above principles, but the big smooth particles which result can damage diaper backsheets. So, SCA has developed a cellulosic or gelatin coating to retard the absorption rate of smaller SAP particles. K-C use divalent metal ions such as calcium to reduce swelling by ionic cross-linking, these links being destroyed as a second additive - a cation complexer such as sodium hexametaphosphate - slowly goes into solution. Dow has used polyvalent ions such as aluminium to create transient ionic crosslinks that retard the rate without affecting the final capacity. Mr Christiansen claimed this approach was capable of giving a SAP with 30g/g capacity and a ten-fold reduction in saline uptake rate.

Superdry Underpads
Janet Wilson of Shiloh Healthcare (UK) compared their Superdry underpads with competitive products based on fluff pulp only, fluff pulp plus SAP, and the original 5-ply tissue based on recycled paper. (The Superdry product uses a thin pre-formed core from Mc Airlaid)
• Fluff/SAP gave the best absorbency by weight (1840gms) but Superdry (1540gms) was second on this basis and best if absorbency by volume was considered
• EDANA strikethough results also favoured the fluff/SAP pads but Superdry performed best on the rewet test - 0.8gms versus 4gms for the fluff/SAP.
• 5-ply tissue gave the best horizontal wicking (2230 cm 2 wetted area). Superdry came second with 1911 cm 2 .
• Superdry costs more than the traditional 5-ply tissue but is easier to use and more comfortable for the patients.
• Unlike the 5-ply tissue product, Superdry has tested free of bacterial contamination.
• The product has recently been introduced on contract to the British National Health Service (annual purchases of underpads put at £5.25million), and several Trusts are now buying it in preference to the cheaper product.

Basic Disposables

Dr Richard Chapas (Consultant) suggested developing sustainable disposable products for marketing to the “base of the population pyramid”, the 4 billion people living on less than $1500/year, 2 billion of whom exist without access to power or petrol. Products for this sector would have to be simple, biodegradable (cellulose based) and manufacturable by systems compatible with the infrastructure of the target region. (“Roll goods to be converted at the village level”)

No Value Added

Andrew Urban III, Consultant , reviewed some classic technical successes that led to commercial failures:
Weyerhaeuser's Giggles™ Diapers used an ultrathin compressed core made by impregnating an air-laid pulp with glacial acrylic acid and polymerising it “in situ”. The resulting superabsorbent was electron beam cross-linked and stripped of monomer using steam. It then acted as the glue to bond the pulp/SAP structure together as it was compressed in a calender. The resulting near-perfect dispersion of SAP in pulp resisted gel blocking and expanded freely on wetting. Sandwiched between coarse polyester subfacing and a textile-like backsheet, in a diaper that in 1985 already featured the first leg gathers and elastic waists, it was superior to the P&G ad K-C products in all but price. Weyerhaeuser test-marketed in Seattle and unexpectedly came up against P&G's more lavish test marketing of their first leg-cuffed diaper, failing in comparison.
Pope and Talbot's retail AI products used an ultra-thin thermally bonded air-laid pulp with high-SAP content at a time (1990) when the competition was bulky (K-C Depends® and J&J's Serenity®) However in this case the P&T range was cheaper and easier to fit and wear discreetly than the opposition. Why did it fail? In Mr Urban's view P&T's marketing and sales efforts had been underfunded.
P&G's Uni-Futur™ diapers , introduced into Mexico in 1995 as an even more cost effective upgrade to their basic low-tech Uni™ diaper. Despite a unique semi-elastic narrow “bikini” shape, the usual lavish market introduction and a 20% price cut, it failed to sell. Apparently consumers could not believe that a product so thin and small could work properly. Worse still, Mr Urban argues this failure adversely affected the Pampers™ name in Mexico causing P&G's share to decline from 20%+ to 10%- in subsequent years.

Evolution at work

Oliver Bittner of Freudenberg Vliesstoffe KG ( Germany ) described how their spunlaid and water-jet-split bico fibre nonwovens could make very good durable industrial wipes. After splitting in hydroentanglement they comprised 0.1 micron fibres which gave better wiping because they could get into smaller crevices on surfaces. The anisotropic fabrics were easy to convert, cuttable in any direction without fraying, weldable and heat sealable. Being made from polyamide - polyester bicomponent filaments they could be washed at 95 o C, bleached and tumble dried many times.

Spunlace progress

Under the heading “New Possibilities in Spunlace” Thomas Fechter of Fleissner GmbH ( Germany ) mentioned :
• A Nomex/PET 2-layer laminate for hot air filters.
• Another hot air filter using woven steel mesh sandwiched in Nomex.
• A filter made of 1.7 dtex PET sandwiched between 6.7 dtex PET.
• A wipe made from 2.2 dtex viscose on top of yellow 1.7dtex PP. This had been patterned, apparently after the main bonding stage, by further hydroentanglement on a drum so that yellow squares showed through on the white side.
• A wipe with a rough side created by a square pattern, and a fine smooth side.
• Cotton pads with a dimpled surface.
• Cotton pads with a wavy jet-line surface achieved by oscillating the last hydroentanglement nozzle.
Efficient patterning on a fully entangled fabric requires three jet strips in a single head so that the jets reinforced each other before any relaxation (disentanglement) can take place.
World production of spunlace in 1999 was put at 240,000 tonnes.

Theoretical Wipes Market

Sabine Martini - Calculated Diaper and Training Pant Demand
After reviewing the 2000 Edana statistics related to wipes growth (152,200 tonnes, of which 78,000 were in personal and baby wipes, 42,000 in industrial, the rest being in household) Sabine Martini (Consultant) calculated the total size of the baby wipe market based on birth rates and the assumption that 8000 wipes were needed for each baby. This figure was in turn based on known diaper sales and the assumption that 2 wipes would be needed per diaper change. A theoretical EU15 market potential of 33.8 billion wipes emerged for 2001, compared with actual sales of 16.7 billion to give a current market penetration of 49%. In Germany , the most developed market, the figure was 56%. In-store price comparisons showed UK mothers paying twice as much for their baby wipes as German mothers.

Air Laid Problems

Ivan Pivko (Consultant) reviewed developments in air-laid nonwovens since Index 99 and speculated on possible developments in the next three years. The key points since 1999 were:
• Massive capacity additions - Buckeye, Concert, BBA ( China ), Main Spa ( Italy )
• No breakthrough in diaper cores to use the capacity, hence overcapacity problems now.
• Rayonier's smaller investment in “Novothin” cores appears to be paying off.
• K-C's move back into air-laid with Cottonelle roll wipes failing to live up to expectations.
• Air-laid being unexpectedly promoted by Georgia Pacific after the acquisition of Fort James .
• Air-laid proving to be less than ideal for the wipes market c.f. hydroentanglement.
• The wipes business passing the $1bn sales mark last year, withv spunlace now moving ahead faster than airlaid.
In the next 3 years:• Airlaid capacity will reach 750,000 tonnes.
• The industry will then pause, reflect and consolidate rather than expand further.
• Costs will be reduced as new investments have their effect.
• Waste reclamation will be improved.
• Air-laid wipes will decline prompting further spun lace expansion.
BUT Will P&G or K-C accept the Buckeye or Concert core products?
• What if aggressive moves into airlaid by SCA or the newly expanded Tyco Healthcare prompt defensive responses from P&G and K-C? (i.e. cornering the Buckeye/Concert capacity)
• Could SCA in return acquire the old J&J air-lay or Georgia Pacific's Minnesota capacity?
• Could Tyco Healthcare, now testing Novathin®, could commit to Rayonier's ideas for a 100,000 tonne line?
• What if BBA acquire Concert?
Asked about his gloomy prognosis for airlaid in wipes, Mr Pivko commented that the product was proving too harsh to compete with spunlace in personal care wipes, and the short fibre content prevented it matching spunlace for abrasion resistance in household wipes.

Another Air-layer

Jean-Philippe Dumon of Thibeau/Asselin NSC Nonwoven (France) introduced AirWeb®, an air laying system intended to take card-web, disperse the fibres in air and lay them randomly in basis weights from 35 to 200gsm without the need for cross-lappers and web drafters. Similar systems from Fehrer and Hergeth were described and said to be in production mainly for make-up removal pads. Mr Dumon claimed a more random lay (MD/CD <1.5) over a wider weight range (35-200gsm) at higher productivity (200-260 kg/hr/m) giving fibre individualisation and web appearance comparable to carded products.

Reicofil IV

Bernd Kunze of Reifenhauser GmbH ( Germany ) revealed the targets for the Reicofil 4 spunbond technology:
• Higher throughput per beam, allowing fewer beams at the same line speed.
• Independent adjustment of cooling, stretching and lay-down sections giving more control of MD/CD ratios
• 5500 m/min spinning speeds for PET and 3500m/min for PP to give line speeds up to 700m/min
• Fiber deniers down to 1.0
• Fabric weights down to 10 gsm.
• Potential throughput up by 22 to 50% over Reicofil 3.

Polyethylene Spunbonds

Dr Derek Budgell of BBA Linotec Development GmbH provided data on the properties of low- and high-density polyethylene spunbonds. When spun on the same system, PE nonwovens gave about a third of the tensile strength of PP, the LDPE version giving about 50% higher elongation, while the HDPE version was about 20% less extensible than the PP. HDPE had a less waxy handle, but LDPE was softest. Both had reduced fibre tie-down and hence lower abrasion resistance than PP. PE is however better in radiation sterilisation than PP because it cross-links to higher molecular weights where PP suffers degradation by chain scission. A major application of spunbond PE is ostomy bag covers where the skin-comfort of the ultra-soft fibre is preferred.

Silane Quat Antimicrobial

Patrick Vandendaele MD of Devan Chemicals ( Belgium ) presented the Aegis paper on silane quat antimicrobials:
• Conventional antimicrobials leach from PP fibres to form, in efficacy testing on agar culture plates, a “zone of inhibition” on which the organisms cannot grow.
• At the boundary of this ZOI most organisms are killed, but the few that survive are those with enhanced resistance to the biocide.
• If cultures are taken of these survivors, and the tests are successively repeated, it has been shown that bacteria can develop complete resistance to the biocide in just three generations.
• The Dow-Corning organofunctional silane compounds (as used in medical nonwovens and consumer textiles since 1976) to create an antimicrobial that bonds to PP with excellent durability. (non-leaching)
• It's a 3-trimethoxy silyl propyl dimethyl octadecyl ammonium chloride on a lipophilic aliphatic chain, also known as AEM 5772 or Aegis Microbe Shield.
• It bonds to the PP through the silyl group and kills bacteria - without being destroyed itself - by physically penetrating the cell membrane with the aliphatic chain “sword” before “electrocuting” it with the charged nitrogen atom on the quaternary ammonium group.
• The compound can be added to the PP spin-finish or padded onto the nonwoven.
• Socks, underwear, bedsheets, waddings and carpets are among the other applications.
• On carpets, it destroys the symbiotic fungi on which the dust-mite depends, and so prevents dust-mite colonies from developing.
• Its presence on a fabric can be highlighted with bromo-phenol blue indicator.
In response to questions:Application temperature governs the wash stability of the antimicrobial: the higher the better, 200 o C being no problem for the chemical. 140 o C is recommended for PP fibres, 170 o C for PET. It attaches by copolymerising to the synthetic fibre surface. On cellulosics the methoxy group bonds just like a reactive dye. The finish typically survives 5 washes at 95 o C. 0.15% add on is recommended for shoe linings with levels up to 0.25% being possible. It can not be added to the polymer melt: must be a spin finish to work properly.

Lamination on a Perforator

Jim Cree (Marketing Manager) and Bill Deep (Global Product Manager) of Tredegar Film Products ( USA ) described how the vacuum-perforation process used to make apertured films could be adapted to produce laminates. Extruding the film-forming polymer onto a PP nonwoven prior to passing the combination, film side down, around the suction drum while the film was still plastic produced a two-layer product. A second layer of film could then be extruded onto the “male” side of the perforated film to give an even bulkier product without perforations. A wide variety of possible nonwovens coupled with a wide range of possible films and several different aperturing patterns led to an enormous array of possible end products. Those mentioned specifically were:
• A 35gsm spunlaced nonwoven laminated to 20gsm PE film to give a 2-surface wiping effect. (e.g. Scouring and absorbing)
• Such wipes held the lotion better than all-fibre wipes (gravity drainage restricted by the film)
• Film laminated to 13 gsm spunbond to give a diaper backsheet.
• Elastic laminates for waistbands, side panels and medical bandages.
• Ostomy bag covers
• A 60gsm nonwoven attached to a 20 gsm film to give an improved strength dry wipe (Swiffer®-type)
The process works best for layers of similar melting points otherwise compatiblisers are needed.

Lamination on a slitter

Alessandrio Celli's (A. Celli SpA Italy ) paper included some details of the hot-melt lamination stage being built, thanks to a collaboration with Nordson, into a full speed slitter/rewinder. On-line lamination of spunbond to breathable film was mentioned.

Compressive Bulking

Richard Walton of Micrex Corporation (USA )explained that it was wrong to think of microcrepeing compaction ratios as stretch in reverse. If a fabric was compressively creped from 100m long to 50 m long, this was a 50% compaction, but when stretched back to 100m under tension, the stretch was 100%.
Richard Walton of Micrex Corporation
He could now build machines up to 3m wide capable of running at 200-300 m/min. Price of a 2m wide unit was ~$500,000 and he was now building these to be operated on-line on an HE wet-wipe machine. Micrex has recently patented an improved process that provides bulk which is resistant to wetting out. In this process, 16% compaction gives:
• 79% more dry thickness
• 66% more wet thickness
• 49% more lotion capacity per wipe
• 26% faster wet out
• 33% increase in absorbency (g/g)
Samples of Micrex-treated and untreated spunlace wipes were provided to illustrate the improvements arising from this simple bulking and softening treatment.

Hot Melts

Alan Ramspeck of Nordson Corporation (USA) elaborated on the three rules for efficient non-contact spray application of hot-melt glues in core stabilisation and elastic attachment:
Larger glue filaments form stronger bonds because, despite the lower coverage at constant weight :
• They retain heat better
• They bridge gaps better
• They flow better to create a bigger bond
Filament crossovers give stronger bonds:• They create a rip-stop effect (its more difficult to start a tear than to propagate it.)
• Double thickness=larger fibres (see 1 above)
• Mini-spirals give more crossovers than larger spirals, (but these crossovers should be at the centre rather than the edge of the spiral pattern.)
Lower Variability minimises waste. This can be achieved by optimising multi-strand attachment by fine tuning of the nozzle-to-elastic configuration. (a 5-10mm pattern width gives good results)
However on very thin substrates, the pursuit of strength and efficiency may be secondary to maintaining a good appearance and handle. Here finer filaments applied at higher frequencies will minimise bleed through and distortion.

Cooler Melts

Bill Leftwich of National Starch & Chemical (UK) suggested that the Coolmelt adhesives used in packaging and bookbinding should be of interest to the nonwovens industry.
Coolmelts have the same range of viscosity as hotmelts, but achieve this at a about 30 o C lower temperature. As a result lighter substrates could be bonded with less heat distortion, 90 o C application temperatures becoming usable in production. Odour levels were lower, and thanks to the adhesive packs being made of the same polymer as the adhesive, packaging waste was eliminated. The products were also proving excellent for core stabilisation and attachment of the newer, more elastic frontal tapes.
However there were several “challenges” to be borne in mind by the converter:
• Bleed through leading to blocking could be a problem if the temperature of application is too high.
• High compression levels in diaper packing could make matters worse.
• Ditto high ambient storage temperatures.
Mr Leftwich concluded by suggesting that the cooler melt products would allow manufacturers to build in more functionality than their hotter counterparts.

Metallocene PP Fibers and Nonwovens

Flemming Stengaard presented the Fibervisions a/s ( Denmark ) paper on novel fibres for value-added nonwovens. In essence these fibres were fine denier PP made from an ATOFINA isotactic metallocene resin on a long-spin line. Compared with the usual Ziegler Natta catalysed PP, the metallocene process gives a narrow molecular weight range and hence finer fibres, a higher molecular orientation, double the tensile strength but with reduced elongation and toughness. A further consequence of the long-spin route is the surface oxidation that yields filaments with a distinct skin-core structure.
The resulting 1.0 to 1.5 dtex fibres perform well in thermal bonding to give more uniform nonwovens with smaller pores and improved softness.
Mr Stengaard pointed out that the metallocene process is still under development and that further improvements could be expected. For instance the second generation of metallocene resins would give properties midway between current metallocenes and ZNPP.
Marc van der Elst of ATOFINA , in a related paper covered similar ground but added data on the performance of the metallocene PP in spunbonds and SMS. The finer stronger fibres obtained from metallocene resins allow the production of lighter spunbonds without loss of strength, uniformity or cover.
Angelo Lonardo of Basell Polyolefins (Italy) said their metallocene catalysed PP resins were superior to the peroxide treated Ziegler-Natta PP because they gave spunbonds with higher tenacity, softer handle, better barrier properties and better uniformity. They also have the potential to be spun at lower melt flow rates. In melt-blown processing, 1200 and 2000 MFR resins had been converted into a range of industrial and hygienic nonwovens. These resins processed better than peroxide degraded ZNPP giving finer fibres, better barrier properties and lower volatiles. Conversion to staple fibres on both long and short spin lines gave better fibres and the potential of improved thermal bondability.

Cotton-Like Flax

Elena Kuchkova of the Russian Nonwovens Research Institute described the use of a soft cotton-like flax fibre to make medical nonwovens using hydroentanglement. Details of the “physico-chemico” process used to prepare this particularly pure form of flax were not provided, but it was said to create surface of amorphous cellulose, capable of high absorbtion and with an ability to inhibit microflora development.
A 50/50 rayon/flax hydroentangled fabric gave 16cms vertical wicking in 20 minutes compared with 12cms for a 50/30/20 flax/rayon/PET blend. (No data on 100% rayon) In a separate trial, 100% rayon fabric gave 10.2gm/gm absorbent capacity while the 50/50 rayon/flax blend gave 11.3gm/gm. In yet another trial a 60gsm “flax-containing dressing napkin” gave 14gm/gm against the rayon control value of 10. Clinical trials were said to indicate a preference for the flax containing dressings because they had lower adhesion to wounds than the rayon/PET controls.

Antimicrobial Acrylic

Roland Cox of Acordis Acrylic Fibres (UK) classed their Amicor™ antimicrobial fibres as “moderately hydrophilic fibres containing additives that are able to migrate”. The two biocidal additives used in Amicor™ fibres are registered with the Biocidals Directive and are unlikely to encounter any difficulties with this new legislation. Bedding products containing Amicor™ were clinically proven to help prevent allergies from dust-mites. Hospital and food-preparation textiles containing Amicor™ had now been shown resist the development of such organisms as Staph. aureus, Salmonella, E Coli, Klebsiella pneumoniae, MRSA, and, in air filtration systems, legionella. The biocidal activity survives 200 washes at 100 o C.

Radiation affects performance?

Mario José Araújo Marques Abreu, a lecturer at Minho University ( Portugal ) reported on the effects of gamma irradiation and electron-beam sterilisation procedures on the liquid permeability and air permeability of surgical gowns. The effects were small, but electon-beam tended to increase the repellency while gamma irradiation increased the air permeability.

Non-isothermal moisture vapour transmission

Ji Young Ruckman of Manchester Metropolitan University (UK) has tested breathable and non-breathable pads both isothermally and with a temperature gradient. She found the temperature gradient allowed very much higher moisture vapour transmission rates – up to 5500 gms/m 2 /24 hours if the product was “non-synthetic”. Synthetic breathable films tended to lose their permeability under non-isothermal conditions because condensation blocked the pores. She found her measurements correlated with her own one-woman wearer trial, and was now planning a 25 person trial.

Irritating Problems

Christine Wild of Cognis GmbH ( Germany ) pointed out that the conventional hydrophilic spin-finishes used on polypropylene have a high potential for irritating human skin and are easily washed off the fibers. Versions conferring more permanent hydrophilicity have been developed and are in use, but these prove unacceptable in long-life products or in products where high or multiple wettings are the norm such as wet-laid processes or wet-wipes.
Cognis has therefore developed Standapol 1345 as an internal additive where FDA approval is required, and Standapol 1474 where the fibres produced must be immediately wettable without further on-line finishing. These resin additives concentrate in the amorphous areas of the polymer and get pushed to the outer surface in hot-stretching. However low molecular weight resins for melt-blowing allow easy migration of the additives to the fibre skin without stretching. Effects of the resin additives on other nonwoven properties such as tensiles and absorbency are negligible but there is a useful increase in fabric softness.
Dr Wild foresaw applications in coverstock and wipes and felt the permanently hydrophilic resins could even be used as the skin on a regular PP core in bicomponents. In a wipes-related absorption test the permanently hydrophilic PP fibres containing the Standapol additive were blended 50/50 with polyester in a spunlaced fabric and shown to have 20% better absorbent capacity than the 65/35 viscose/PET control.

Drape analysed

Chang Kyo Park of Chonam University ( Korea ) has used image analysis to extract more information about fabric drape (e.g shape and number of folds) from what was, in essence, a Cusick drape tester.

Fantasy fibres

Dr Giuseppe Salvio of Montefibre ( Italy ) described new “multifunctional” polyester fibres obtained by combining otherwise well known premium features. Antimicrobial flame retardant fibres and coloured flame retardant fibres were the two examples given but clearly there are many other possibilities.
C R Woodings April 2002