Imagine the Future of Viscose Technology 2002

 

Two hundred and twenty delegates attended this tri-annual meeting arranged by Lenzing Technik, the plant and process engineering division of the fiber company. Most of their customers, i.e. the world's viscose makers, were in attendance as were the main suppliers of pulp, additives and finishes. Perhaps surprisingly, there were no users of viscose fibers to be seen.

Keynote Speech

Prof. Wilhelm Albrecht aired the now familiar theme: Unlike oil, cellulose is a basic substance of life which will still be around at the end of this century. The viscose process is the most versatile way of turning cellulose into fiber, but further progress is needed to reduce its environmental impact and increase the efficiency of the derivatisation step. To this end he called for:
• More work on activating the cellulose to improve its reactivity. Electron beam treatment had been shown to be effective, but the mechanism of the effect remained to be understood.
• The development of much faster spinning processes.
• Further moves towards an emission free, closed-box process.
• The development of “just-in time” delivery of spun-dyed viscose (days rather than weeks between order and delivery)
• The development of spun-bonded viscose processes to compete with the spunbonded synthetics in nonwovens.
• Further development of fiber reinforced plastics.
• The development of cellulose-synthetic composite fibers.

Trends in Asia Viscose Markets

Craig Barker, President Director of PT South Pacific Viscose identified regional agreements such as NAFTA and the Caribbean Basin Initiative as outweighing the World Trade Organisation where tariffs were concerned.
• Mexico now supplied the US with twice as much textile as China , up from half the Chinese level in 1994. China was now in third place. Canada exported more textiles to the USA than China since 1999.
• The EU is similarly shifting textile imports away from Asia to Eastern Europe and North African countries.
• Asian producers can no longer assume that their cost advantages guarantee success in exporting to the West.
• Textile production capacity is moving rapidly to countries with even lower labour costs and to countries with grants encouraging industrialisation.
• Asian producers must now look to their domestic markets for growth, and must upgrade their spinning and weaving if they are to compete.

With regard to Indonesian viscose, three modern plants supply high quality fibers to support downstream textile production, most of which has been exported in the form of higher value spun yarn or fabric. 90% of output goes into apparel related markets. Asked about nonwovens, Mr Barker said that a regional nonwoven industry was lacking and that the standard of living needed to rise before this market would be of significance to the Indonesian viscose producers. “You need a kitchen before you need a kitchen wipe”.

Viscose Production In China

Yuan Zhiguang, Divisional Chief of the China Chemical Fibers Association said that in 2001 China made 450,000 tonnes of viscose staple in factories which were 84% state owned, and 126,000 tonnes of filament in factories which were 97% state owned. Imports of viscose staple were 49,000 tonnes in 2001, down from 187,000 tonnes in 1998. By 2005 it targets a staple fiber capacity of 570,000 tonnes and expects to produce 505,000 tonnes. In 2000, the industry imported 176,000 tonnes of cotton pulp to make viscose, but in 2001 the figure had fallen to 88,700 with imported woodpulp making up the difference. One of the key environmental problems of the Chinese viscose industry was identified as the effluent from their cotton bleaching/pulping operations. Another, giving economic problems as well, was the abundance of small (<15,000 tpy) plants. They now plan to build two new viscose plants.

Viscose Production In Japan

Mr Hirata of Daiwabo Rayon reviewed the viscose business in Japan . Only two producers remain, Daiwabo with ~30,000 tpy capacity and Omikenshi with ~20,000 tpy. ~10,000 tonnes were imported in 2001, the vast majority from Indonesia in the form of spun yarn.

Daiwabo's strategy is to try to survive as a viscose producer until the effects of oil-shortages begin to affect the synthetics. To do this they will:
• focus on special high quality products
• seek ways to reduce pulp costs (fast growing hybrid species)
• rationalise production – Lenzing's compact SXS system (see later) mentioned as becoming more necessary.

With regard to markets, nonwoven use of rayon in Japan moved ahead of textile uses in 2000, and reached 24,000 tonnes in 2001 compared with ~20,000 tonnes for all other uses. 80% of the nonwoven rayon is in hydroentangled products, mainly wet-wipes. Prices to nonwoven customers were now higher than to yarn spinners, but the quality demands were higher also. Daiwabo expects to develop new fiber types to allow new higher value nonwovens. Needless to say further growth in this sector is expected.

N.B. one of the graphs presented referred to “normal rayon staple”- ~43,000 tpy as well as “total rayon staple” ~65,000 tpy. This implies there is an additional 22,000 tonnes/year of special rayon staple, not included in the above statistics. This is most likely the polynosic rayon from Toyobo (Tufcel®) and Fujibo, both of which shut down in autumn 2001

A low-cost lyocell substitute?

Mr Xu Bin of China's Dandong Chemical Fiber Plant covered their acquisition of the Toyobo Tufcel® polynosic technology and equipment, and how, with the help of Lenzing Technik they planned to produce 15,000 tons/year of polynosic staple. The approach appears to be to replace the old spinning machines with the Toyobo Tufcel® spinning machines, buy in some new filters, shredders, blenders and wash machinery, and be in a position to produce a lyocell-like fiber with much lower capital costs.

Asked through an interpreter if this meant the Chinese lyocell strategy was less likely to go through as previously thought, no clear answer was given. Being told (by Prof Albrecht) that the polynosic process was much more polluting than lyocell, Mr Xu was unconcerned. The main motivation of the approach was economic.

Spun-Laid Viscose Nonwovens

Osamura Kida of Futamura Chemical Industries ( Japan ) gave a rare public presentation of the spun-laid viscose nonwoven process they use to make TCF fabrics. They spin the “thermoplastic” hydroxymethyl cellulose xanthate fibers from a polynosic viscose – the etherification resulting from adding the “necessary chemical” to the spin bath. The fibers are stretched, cut and fed to a wet-lay machine. The sheet is then thermally bonded, bulked and regenerated back to cellulose prior to washing drying and wind-up. One slide (no prints of the slides were available) showed a fiber section with a thick HMCX outer layer concentric on the usual CX core, this being distorted in stretching on a drum to pull the core to one side. This asymmetry was said to give the high crimp in the bulking stage. End uses in medical (gauze replacement), hygienic (wet-wipes), cosmetic (make up removers) and industrial markets (filters) were quoted. A comparison of a 40 gsm airlaid viscose (unspecified bonding method) with 40gsm TCF showed the spun-laid version had triple the dry strength and quintuple the wet strength in both directions.

Trilobal Viscose from Lenzing

Josef Schmitbauer of Lenzing R&D ( Austria ) pointed out that the normally used measures of absorbency for cellulosic fibers do not correlate with the absorbency of tampons. Lenzing therefore recently introduced what they called the novel methods of making tampon-shaped compressed plugs and testing them on a Syngina to optimise fiber properties. Their work showed that a trilobal viscose performed best, and further work optimised the shape into something looking remarkably like Acordis' Galaxy.

Two interesting observations were made along the way:
• When designing the spinnerets, Lenzing's computer modelling found that it was best to have one of the limbs of each hole aligned along a radius to get more consistent acid distribution.
• Syngina absorbency correlated with pulp type: the expensive pre-hydrolysed kraft pulp made from hardwood by an elemental chlorine free process being best (18.8 and 19.8 g/plug), and that made from hardwood by an elemental chlorine-free sulphite process being worst (18.2g/plug).

Comparisons of a 3dtex Viscostar® trilobal fiber by Lenzing with their 2.8 dtex viscose showed a Syngina benefit of 17%, rather less than expected on the basis of Acordis work.

New wet-opener system

Breaking up the highly cohesive wet fiber bed after washing and mangling in order to lay an even bed in the dryer has long been one of the problem areas of viscose staple manufacture. If the opening is too vigorous, the fragile wet fibers are broken and/or entangled. Hans Weber of Lenzing Technik described their solution: a gentle full-width wet-opener roll, fed with 10,000 m 3 /hr of air at 160 0 C. On a 50 tpd production line (in the USA ) this reduces the moisture content by 20% making the fibers stronger and significantly more easy to open. It also improves the evenness of dryer bed formation and increases the drying capacity of the production line. It also eliminates the wet-hopper and spiked lattice dryer feeders which have been a significant source of contamination since they were first thought of.

Therapeutic fiber

Liu Zhong, VP of the Yibin Grace Group (Chinese viscose filament producer – 24,000 tpy) described a new silkier viscose yarn, essentially an alloy fiber made by mixing “pod-protein” into viscose. Pod-protein contains 18 amino acids (MWt 10,000 to 200,000) and can be dissolved in dilute alkali to give a stable dope which blends easily with viscose. When spun in the usual way, the proteinaceous component migrates to the skin region giving a bicomponent fiber where the protein is efficiently hydrogen bonded to the cellulose. An analysis showed a total of 12.8% of the amino-acids in the finished fiber, and the claims made for it in skin contact were:
• Promotes cell metabolism due to serine, threonine and leucine.
• Heals wounds faster.
• Prevents skin ageing.
• Protects the skin from the adverse effects of sunlight (alanine content).
• Prevents skin diseases “e.g. skin tickle”
• Therapeutic effect on scapulohumeral periarthritis, rheumatoid arthritis, and gastropathy.
• Keeps dry skin moist.

However, while having tensiles between silk and viscose, its properties are destroyed quickly by bleaching and slowly by sunlight. It was impossible to elucidate the nature of the pods during the Q&A, but in private conversation they were said to be the pupa or cocoons of the silkworm which had been sorted to eliminate the “dead and rotten pods”.

Viscose Casings

Dr Heinrich Henze of Casetech GmbH (a division of Bayer) presented the history of casings, or, as he quipped, tubular viscose fibers with diameters of between one and ten inches. The one-inch diameter casings had been developed in the ‘40's to form hot dogs and were stripped off before they were packed.

The larger sizes were mainly for salamis, and these were typically fiber reinforced, being produced by coating and regenerating viscose on either side of a wet-laid nonwoven as it was formed into a tube. Nowadays, barrier coats were added as well, either inside or outside the tube.

Western markets for casings are declining, but South American and Asian markets are growing. Different attitudes to meat-eating and BSE are behind the trends. Plastic casings are gaining share, but these are hard to remove, impermeable to smoke and moisture and fail to give the traditional appearance needed for the high quality market. Viscose-based hot-dog casings still account for over 50% of the total market.

Asked about the lyocell casings project undertaken by his competitor (Viskase) he commented that the resulting tubes were good, but that the project failed for NMMO-recovery reasons.

Cationic Cellulose

Alexander Brandner of Cellcat ( Austria ) described their cationic cellulose fibrids made by injecting cationinc polymers into viscose prior to mixing with sulphuric acid in a disc refiner. The resulting fibrous precipitate is collected and washed on a band-filter and sold as a moist off-white crumb for use in papermaking where it improves runnability and retains additives such as OBA's in the sheet. Savings of up to 50% more OBA than achievable with polyamines were claimed. Cationic charges of up to 2000 micro-equivalents/gm and Schopper-Riegler values of up to 90 0 were achievable.

Carboxymethyl Cellulose Markets

Dieter Lehner of Mare Austria GmbH provided an overview of the global market for carboxymethyl cellulose. Of the 300,000 tonnes used in 2000:
• Europe used 37%, North America 31%, Asia 26% and Latin America 3%
• The food industry used 22% as a thickener, stabiliser, moisture content regulator, suspending agent (prevents crystals in ice-cream), and fat-content substitute.
• The oil industry used 20% to control the properties of water-based drilling mud.
• The pharmaceutical/personal care industry used 12% as a thickener, foam stabiliser and binder.
• The paper industry used 12% as a binder and as a formation and surface improver.
• Detergents used 6% to improve washing power, to protect fiber from acids and to stop dirt sedimentation. It is also used in detergent tablets as a disintegrant.
• Textiles used 6% mainly in sizing synthetic yarns.
• The remaining 24% was split between wallpaper adhesives, water-based paint thickeners, ceramics, and ore floatation.

CMC will lose some of the food market to natural thickeners like guar-gum, pectins, and alginates, and to some synthetic thickeners. On the other hand its use will grow to replace fat in low-fat foods, in new applications in the pharmaceutical and personal care sectors, in papermaking as more recycling occurs, and in increased oil-exploration. Overall 2-3% annual growth is forecast. Asked about CMC's use in alloys with viscose, Mr Lehner admitted to a project with Lenzing where cross-linkers were being used to improve its retention in spinning and washing.

Dynamic Surface Tension

Anders Cassel of Akzo Nobel ( Singapore ) described their work comparing Dynamic Surface Tension (maximum bubble pressure method) with Equilibrium Surface Tension (De Nouy method) of viscose spin-baths containing their additives. Beyond “the DST of the spinbath is related to the concentration and type of surfactant added”, hard conclusions were in short supply, but their additives were said to look even better by the new technique. Perhaps most interesting was the fact that a viscose modifier (Berol Visco 32/315) was a good DST reducer, leading to speculation that it assists more rapid dispersion of gas bubbles from the viscose in spinning, and thereby contributes to the modifier effect.

The DST equipment (a Sita t60® bubble pressure tensiometer) is cheap and reliable and can be used on-line.

Sulphuric Acid from Waste Gases

Peter Björklund of Kvaerner Chemetics, Sweden described how the pulp industry now burnt sulphur containing gases and made sulphuric acid from the resulting sulphur dioxide stream. Used in the viscose process this could reduce sulphur emissions and reduce the need for new acid. According to a viscose producer present, better processes were already in use, and the maximum saving of acid would amount to about €0.05/kg fiber.

Maybe the better process was the Sulphox system covered later by Walter Kanzler of Kanzler Verfahrenstechnik . Using similar principles this process was said to be in use in several European viscose plants and had worked well for up to six years.

Both of these incinerator systems required fuel injection to burn the gases. One chemical engineer said the best approach was simply to feed the gases into the sulphur furnace of the standard Contact acid manufacturing process in use on most viscose sites.

Bacteria cleans up waste

Karel De Waal of Bioway ( Netherlands ) showed how bacteria could deal with CS 2 in waste gases. The recently developed strains were happy at zero pH and fed on gas with 150-3000ppm of CS 2 (and other unspecified nutrients) they excreted 2-3% sulphuric acid for a cost of about $1600 (sic) per tonne of CS 2 processed. The method was in use to clean up pesticide production effluent and they were now demonstrating its applicability to rayon and sponge production, hoping to reduce the costs/tonne CS 2 to about $250. The sulphuric acid is unfortunately too dilute to reuse in fiber production, so they recommend conversion to gypsum.

Wolfgang Ott of Acordis Kelheim felt that their Biohoch® reactor was the best available technology for cleaning viscose process wastewater. Since installing the first one in 1981, their COD (t/day) in effluent fell from 12 to 8, and the second unit installed in 1991 reduced it further to 2 t/day. They too add nutrients to the bacteria which were said to be unaffected by the 2 mg/l Zn in the stream.

Miscellaneous papers

• Autefa advertised their automatic baling presses
• Sniaco Engineering promoted their yarn spinning system
• Lenzing showed how easy it was to reduce steam and cooling water use in spin-bath recovery by buying their multiple effect evaporators and crystallisers.
• Enka described how they reached 500m/min spinning speed in yarn production using a machine which proved too expensive to be economic.
• Lenzing described their new video microscope linked to image analysis for quantifying particles in viscose.

Calvin Woodings

12 th June 2002

Imagine the Future of Viscose Technology Photos: 4-7th June 2002,

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Nonwoven Technology Conference 2002 – Ottawa 13-16th May

This conference, organised by Marketing Technology Service of Kalamzoo Michigan, USA , and held in a dull and chilly Ottawa, Canada, focussed on the air-lay process. A truly international audience of 200+ delegates was treated to a first-class collection of papers and a surprisingly informative tour of the new, but fully operational, Concert air-lay plant in nearby Gatineau Quebec.

At the start, the audience was saddened by the news of the death of John Mosgaard, the founder and President of Danweb Forming International A/S, and one of the best known speakers on the nonwoven conference circuit. He and his regular contributions to these industry gatherings will be sorely missed. At the end, to the great credit of the closing speaker and conference organiser Jim Hanson, the hall was as full as at the start.

Highlights

• Pre-formed airlaid cores still await a major diaper application. The need for a significant cost benefit over in-situ forming now seems to be accepted.
• After recent installations of new lines; 5 in the last year in the US alone, annual capacity now exceeds the estimated 350,000 tpa demand by about 130,000 tonnes.
• According to Reiter-Perfojet, 60gsm wipes made from 50/50 spunbond PP/Pulp and spunlaced would be half the price of current carded viscose/PES blends.
• Diaper production rates of 3000/min/machine were now possible if preformed cores replaced drum-formers.
• A major US wipes producer would be switching from airlaid to spunlace.
• More details of a new low-cost airlay former said to be capable of handling up to 50mm fibers at over 1 tonne/m/hr emerged.
• A new plaiting system for airlaid core promises significantly higher run-times than the current festooning or spooling systems.

Air-Laid Supply and Demand

Pricie Hanna (John R Starr Inc) predicted a 4.4% annual growth for airlaid nonwovens in wipes for the next 5 years. Sales would increase from 6.2 billion m 2 in 2001 to 7.7 in 2006.
• In 2001, half of all airlaid was latex bonded, a quarter thermal or multibonded and just over an eighth was the K-C Coform process. Hydrogen-bonded and spun-laced airlaid made up the remainder.
• By application, 55% went to wiping, 30% to pre-formed cores – mainly femcare and subfacings - and the rest into tabletop, medical, packaging etc.
• Reviewing nonwoven technologies used in wipes she pointed out airlaid is now in the second rank after spunlace: airlaid still dominates in the USA but spunlace dominates globally. (75% of all airlaid wipes, but only one third of all spunlace wipes, are used in the USA and Canada .)
• The trend to spunlace would continue, even in the USA where a major supplier was contemplating a switch from airlaid.
• “Airlace” – or hydroentangled carded fiber/airlaid pulp laminates was expected to grow rapidly to fill the perceived gap between airlaid and spunlace from both cost and softness aspects.
• Overcapacity would affect the industry for the next year. North America alone had added 5 lines (100,000 tonnes) in the last year, and while Buckeye and Concert were switching products to the new lines, there was underutilised capacity on the older machines.
• The main growth opportunities seemed to be in the less developed countries where a strong demand for modern femcare was arising. Unfortunately this demand was most likely to be met from production units closer to these markets: Mercosur , Turkey , Middle East , China being mentioned.
• To make matters worse, the US need for airlace would be met by European/Middle East imports in the near future. So airlaid profitability would suffer until supply and demand were more nearly in balance.

In response to questions, Ms Hanna commented that there was a lot going on in diaper cores that had yet to reach the public domain. The development of long-fiber airlaid technology to compete with carding looked a promising development (see later). Wet-toilet tissue would progress slowly. While this was a great disappointment to many, she felt K-C would use the plant to make products other than “Cottonelle” while the shortfall existed.

Airlaid History I

Bill Stevens (Consultant) reviewed the early development of airlaid technology, identifying Karl Kroyer as the visionary who first commercialised “dry-formed paper” and offered machinery for sale. Kroyer sold the technology to M&J in 1981, but in 1975, John Mosgaard left Kroyer and set up Scan-Web (renamed Dan-Web in 1981) to commercialise his own air-laying ideas. Independently, Honshu Paper (now part of Oji Paper) developed and commercialised a third process that they kept to themselves apart from licensing J&J.

Current airlaid capacity was put at 480,000 tonnes/year excluding the vertical operations of P&G, K-C, PGI etc, for a market demanding about 350,000 tonnes. This came from 50 production lines making 18 different product lines. For the future, Mr Stevens saw:

• Hydroentangled airlaid as a key area for growth with 6 companies operating the combined processes this year and a further 3 lines coming on stream in the next.
• Hydrogen or X-bonded (calendered without any other bonding agents) airlaid offering greater economy due to easier waste recovery.
• Baby diaper producers needing an even cheaper product before they would be willing to write-off current assets.
• Prospects for growth in agricultural markets at the expense of spunbond.
• Prospects for airlaid/meltblown combinations now that the K-C patents had expired.
• Products utilising the reactivity of cellulose in airlaid.
• The need for fully biodegradable products from renewable resources.
• Increased use in a variety of packaging applications.

In response to questions,
• The Merfin “Band-Aid” development failed because the latex bonded product proved too stiff compared with the incumbent needled viscose pads. (he thought that this would no longer be the case: latexes were now much better.)
• The “nit” problem had been solved mainly by the pulp suppliers developing pre-softened pulp for easy defibration.
• The main problem of the diaper core was now cost: reducing raw materials wastage was the key to its solution.

New Air-Lay system for Longer Fibers

James Westphal (Troika Nonwovens) introduced two new machines: a fiber mixing system applicable to any air-lay process and a new air-lay head capable of handling fibers up to 50mm in length at higher throughput than woodpulp. Both machines used the principle of rapidly rotating spiked rolls to keep the suspension of fiber in air “fluid”. In the air-lay head these replaced the static screen which has been the main bottleneck of the Kroyer-based systems.

The “GreenMat Star Fiber Mixer” was fitted into a line between the hammermill and the forming heads and was fed with pulp, recycle from the former, edge trim and bico fibers. In effect it replaced the transport fan, kept out of the hammermill those materials that could be damaged or reduce its efficiency and achieved very intimate mixing of all components. The payback came not only from the recycling element but from the ability to achieve strength specifications with lower levels of bicomponent fiber. On a 15000tpy line reducing the bico usage from 25% down to 15% would save $3.5M per year. ($350,000 per % bico eliminated)

The new air-lay head or Star former (USP 6233781-B1) had been developed by ME Consulting – Aarhus (ex Dan-Web) as part of a project with the Danish Department of Agriculture to process flax into insulation board. Here Mr Westphal, who had been retained to help commercialise it, revealed that when used in conjunction with the mixer described above it could handle a tonne of fibers/metre/hr irrespective of length in the 4mm to 50mm range. Woodpulp, for reasons unclear, was restricted to half this productivity. Basis weights claimed ranged from 25 to 3000gsm. Asked about handling SAP, he said the powder could be added between forming heads or to the mixer. The mixer tower as currently designed would also handle a tonne/hour of fiber.

With regard to fiber types processable, the gap setting of the star-forming rolls could be adjusted to suit the fiber. Cotton was not a problem. MD/CD ratios were typically 2:1. Troika is now working with a well-known producer of spunlace equipment to develop lightweight formers for nonwoven production.

Airlaid History II

Jesper Dobel (Danweb Forming International A/S) introduced the 3 rd generation air-lay drum former:
• Capable of giving “tabletop” quality free of nits and lumps
• 400 m/min operating speed
• 400 kg/m/hr output

Their pilot line was capable of 600m/min and they were now targeting 800m/min with 1000m/min thought to be ultimately achievable.

He claimed 50% of the installed airlaid capacity for Dan-Web and Dan-Web Technology compared with 43% for M&J.

Installations from 2000 on included:
• the 2.2m line at MAIN Spa in Italy .
• Concerts 2.7 m line in Canada .
• Orlandi's 3.6m former on the HE line.
• Rayonier.
• Kinsei.
• Nanking ( China ) 2.2m line.

Asked if diaper makers would install their own airlaid core line, Mr Dobel thought not: the technology does not integrate well with diaper production, and diaper makers would lose flexibility if they made their own.

Airless Spray Latex Bonding

Paul Scott (Vinamul Polymers) described the fruits of their collaboration with Nordson to develop an airless spray bonding system for uniform application of latex in concentrations up to 55% solids. Cross-cut spray nozzles were fed with latex at pressures between 100 and 1500 psi to give very precise surface coating (at ~50% solids), or penetration through the thickness of the pulp (at ~15% solids). Penetration depth could be adjusted by varying the dilution of the latex. The airless technology saved latex, reduced drying costs and reduced line contamination compared with conventional spraying. The system is already in commercial use on card-webs and spunlaid webs, and has been successfully tested on the M&J airlaid pilot line. The system worked best when heated latex (up to 130 0 C ) was sprayed, and this could mean the approach would work with low-melting polymers also.

Uniformity of application was checked by visual inspection of the spray pattern using special illumination. In the pilot trials, coloured latex was used.

Under-Utilised Technology?

Tony Butterworth (Consultant) dealt with the evolution of airlaid up to 1985, using expired patents to bring out a number of issues that are still relevant today:
• Fluidised bed technology is important. Fibers pass through vibrating screens much faster than through static screens. USP 4144619 describes a process where the brushes also vibrate the screen by beating it.
• USP 3859205 describes a device for separating a pulp/air mixture into three particle size fractions, the coarsest of which would be returned to the hammermill.
• USP's 3886629 and 3781150 cover the essentials of the superior Honshu forming system and starwheel disperser.
• USP's 3606175 and 3825381 (Kimberly Clark) describe air-laying direct from a pack of pulp sheets being ground away on a toothed drum.
• USP 3994047 describes an air-lay version of the dual-headbox Vertiformer.
• USP 4130915 describes the Fehrer K12 card with air-doffing operating on both pulp and fiber simultaneously.
• USP 3984898 describes Honshu 's method of air laying a viscose fiber/pulp sandwich with 3gsm viscose skins.
• The Rando Duo-Feed (USP's 3512218, 3918126) and the J&J Dual Rotor (USP's 3772739, 3740797, 3895089, 3963392) both deal with simultaneous processing of pulp and textile fibers to give homogeneous or two sided products, or multi-layer products with the textile fiber surfaces.
• Describing the J&J version of the Honshu technology, Mr Butterworth mentioned that the long-fiber could be layed onto rods above the forming wire giving a corrugated structure, the valleys of which could be filled with pulp.

Two-Layer Air-Lace Technology

Daniel Feroe (Rieter Perfojet) covered the difficulties of spun-lacing a pulp/long fiber mixture:
• The card web must be pre-bonded on a drum system to give it enough integrity to act as a filter for the pulp layer.
• The pulp needs to be hydroentangled on a flat-wire section with 8 to 10 injectors.
• The injectors work from low to higher pressure in easy steps to ensure that the pulp is entangled with minimal wash-through.
• These injectors need to be widely spaced to prevent any interference due to splashing.
• Even with these precautions, 4-5% of the pulp is lost through the wire and has to be removed - and discarded - before the water can be reused.
• An Air-lace line would require significantly more capital (€17.2M) than a card-only HE line (€9.2M). The additional cost arose for the pulp former and the more complex water filtration system.
• Such a line would be less flexible than a card-only line and in practise would have to be dedicated to very few similar products

So why bother? Because pulp is about one third of the price of viscose and great savings can arise by using it as a substitute. Compared with a 50/50 viscose/PET wipe costing €2.65/kg, Air-laced 50/50 Pulp/PET would be €1.89/kg.

Mr Feroe could not recommend trying to make wipe fabric with fiber either side of the pulp. This is because the first fiber layer would be too thin to act as a pulp filter.

Rieter Perfojet had also investigated combinations of their spunlaid process, airlaid pulp and hydroentanglement. Here the capital costs of a line were €21.7M but this approach gave the most efficient way of combining long-fiber and pulp at the lowest possible conversion cost (€1.32/kg for 50/50 spunlaid PP/Pulp at 60gsm).

In answer to questions, Mr Feroe added that at present there was no way of reclaiming the pulp washed through into the filter system. Spunlacing spunlaid webs was not a problem and needed only slightly more pressure than spunlacing staple. Finally all spunlaced systems needed chemical treatment of the water to prevent growth of microorganisms.

3000 Diapers/minute?

Mike Jelinsky (Martin Automatic) plotted the output of diaper machines over the last 30 years and found it roughly linear from 150 to 650 diapers/min. Extrapolating, he concluded that 850/min would be possible by 2010, but postulated that if cores could be delivered to the line in web form rather than being made in-situ, then 3000 diapers/min would be possible. He listed the other advantages of pre-formed cores as:

• Less waste for the diaper maker
• Easier start up after interruptions
• Energy savings, noise reductions and reduced levels of airborne SAP dust due to the elimination of hammer-milling.
• Lower capital costs: drum-forming now accounts for 15 to 20% of diaper line costs.

With regard to other possible bottlenecks on the diaper line:
• Adhesives application was capable of 3000 diapers/min now.
• Packing (15 diapers/pack) would already run at the 3000 rate.
• Process controls would work at the 3000 rate.

However, with current diaper orientation the 3000 rate could only be reached by making two diapers side-by-side on the same line, i.e. running at 1500 “doubles” per minute. Making diapers sideways on would make the 3000 rate possible on a singles basis.

Asked about the speed limit of running webs, Mr Jelinsky said that their Airnertia rolls would allow tension controlled unwinding at up to 2200 ft/min, at which speed the aerodynamic drag on the web became a significant source of uncontrolled tension. Dusting of the preformed webs would also become an issue at these speeds. Could drum formers be speeded up to allow 3000/minute? Maybe, but it would be cheaper to use preformed airlay.

Airlaid History III

Henning Skov Jensen (M&J Fibertech A/S) provided a catalogue of the new products possible with M&J forming technology, revisiting some themes of his presentations of the last couple of years:
• Binderless airlaid based on calendered long fiber pulps.
• Cotton-linter (70%) and Bico (1.5 den/3mm) airlaid
• Pulp/bico airlaid, spunlaced and through air bonded
• 100% pulp spunlaced from both sides (adequate dry strength but very low wet strength)
• High loft wadding based on 80% 6.7dtex, 6mm PET bonded with 20% of 4 dtex 6mm PET bico.

Line configurations now possible included one or more of thermal, latex, steaming, and calender bonding of single or multi-layer airlaid in combination with carding, spunlaying, meltblowing and glue lamination. The 5-layer diaper core concept, methods of reaching 2.5 tonnes/hr/m output and the Super-site concept were also mentioned.

17 installations of complete M&J lines were listed, along with the three air-formers on hydroentanglement lines at Albaad, Spuntech and Tenotex.

Frank Phillips of Source Options Consultants chaired most sessions.

In response to questions, Mr Skov Jensen said:
• M&J could guarantee profile control to better than +/- 3% over widths up to 5 m.
• Fiber losses when spun-lacing 100% pulp depended on the type of wire used.
• SAP levels could be 10-15% lower when preformed cores were used in diapers.
• SAP levels of up to 60% were possible if a carrier sheet was used.
• Nits could be recycled through the hammermill.

Why spunlace 100% pulp when hydrogen bonding was possible? Because spunlacing gave a much lower density product.

Would a fluff-free core be possible in future? Mr Skov-Jensen thought not.

Economics of Waste Recovery

John Cork (IBIS International Inc.) pointed out that the trend to larger machines using multibonding, or more specifically reduced levels of latex bonding, increased the scope for waste recycling on-site at the air-lay plant. A 20,000 tonne/year unit working at 90% material efficiency could be wasting 2000 tonnes, or about $1million, in pulp value per year.

Latex bond air lay (LBAL) trim and waste – typically 15-25% latex content - tended to gum-up the shredders used to breakup 100% cellulose products and could not be recycled economically. If, as in the thermal or multi-bonded products, levels of latex below about 5% were used then recycling on-line became possible. The key piece of equipment used was the sort of shredder common in other waste textile reprocessing operations. This could be obtained from Temafa or Hollingsworth set up to deal with the airlaid material. IBIS would provide a complete system to deal with all waste from a 20000 tonne plant for about $1M giving a best case payback of 1 year. This would require 2 operators per shift on a three shift system.

In response to questions he said the payback was based on recycling everything back into the process on site and valuing it at fresh pulp price, assumed to be $750/tonne. His reclaim units in diaper and femcare plants could however also separate and recover the SAP, and with TBAL, there was some value to be credited from the slight reduction in fresh bico needed when recycling was in use.

Asked how much of the reclaimed product could be recycled before product quality suffered, he guessed 10-15%. However he was aware of a diaper producer making diaper cores out of 100% IBIS-recycled diaper waste from a nearby larger diaper plant.

Calendering Airlaid

Johannes Walterfang (Eduard Küsters Maschinenfabrik GmbH & Co KG) described the functions of a calender as:
• To reduce the thickness of a web for the next processing step
• To calibrate, or define and set the final thickness of a fabric to meet a thickness specification
• To emboss and add surface interest and aesthetics to a fabric. Embossing could also add functionality e.g. guiding liquid flow.
• To polish one or both sides of a fabric
• To thermally bond a web, pre-heating being needed for thicker products such as airlaid.

Roll materials could be steel, rubber coated or textile coated, and the other key variables were speed, temperature and nip pressure (or gap setting). High nip pressures resulted in deformation of the calender rolls, a deflection of up to a millimetre being possible over a 3 metre wide roll, giving unacceptably high pressures at the edges compared with the middle. This could be compensated for by crowning the rollers, crossing them at a slight angle, bending them, or best of all by using Küsters “swimming roll” system. Here the bottom roll was filled with hydraulic fluid which could be pressurised to deform the surface shape to match the distortion of the top roll over a wide range of nip pressures. For use on air-lay machines, bearings and drive systems had to be protected from the dusty environment, and the rolls were often horizontally opposed to minimise strain on the weak web as it transferred into the nip. Asked about pressures used, 200 N/mm of nip was the maximum. Temperatures ranged from 80 to 250 0 C, spunbonds down to 6gsm were being calender bonded, and brushes could be fitted to keep the rolls free of deposits. Calenders with special engravings could be used to perforate card webs, but holes were normally regarded as a problem.

Fluff fiber Morphology

Denis Sens (Tembec Tartes S.A.- France) pointed out that the naturally hollow fibers extracted from wood had widely differing morphologies depending on whether the tree was deciduous or coniferous, grown in the cold north or the warm south, and whether pulp was made from forest thinnings and roundwood or from saw-mill waste.

The key aspects of pulp fiber morphology were length, curl and width (if collapsed) or diameter (if still hollow). Tembec now measure these properties using the Techpap Morfi LB 01 analyser which scans a flowing suspension of fiber at the rate of 4000 fibers in 3 minutes. Hollow wall thickness is important and this needs a separate evaluation on the Metso Fiber Lab 3 instrument.
• The faster growing southern softwoods have been shown to give longer fibers with thicker walls and hence fewer fibers per gram.
• Levels of curl are similar, but sulphite pulping gives higher curl than the Kraft process.
• Tembec Tartas now make different pulps from juvenile and mature southern pine, the mature giving longer (2.5mm versus 2mm), coarser (38 versus 28 mg/100m) fibers and the airlaid producer can select which is best or buy a blend of the two.

TT also makes specialities which they hope may prove of interest in higher value air-lay products:
• Cotton linter pulp (1.8mm fiber with 25mg/100m coarseness) normally used for cellulose derivative and speciality paper manufacture.
• Cold caustic extracted cellulose (a mercerised 1.8mm fiber with 34 coarseness and a high curl of 25% - up from 15%) normally used for cellulose acetate production and filter papers.
• Cross-linked Cellulose (2.3mm with 40 coarseness and 24% curl) made to stay bulky when wet.

Finer fibers give better softness, strength, rewet and printability. Coarser fibers give better acquisition rate, total capacity and porosity. Debonders make the fiber behave as if its finer while cross-linkers make it behave coarser. Hardwoods like eucalyptus tend to be too short and dusty for use in airlaid.

The Future of Festooning

Roberto Rahn (KorTec GmbH) compared the festooning systems developed by Gevas and KT Industries with the original KorTec process and a new KorTec process developed specifically for diaper core weights. The technology of festooning could be either single-lane (one endless ribbon per packed block) or multi-lane (as many ribbons as the width of the packer would take, splicing being used to join up the ends to create a single ribbon.) The multi-lane system required a rotary drum folder to build the pack, whereas the single-lane system could also use swivel-arm layering or KorTec's new plaiter machine.

Current single-lane systems were poor for narrow ribbons (30mm), while the multi-lane systems were not viable for heavyweights (>450gsm diaper core). KorTec's single lane plating system which used a complex cross-folding belt mechanism to build a much larger package than possible with swivel-arm or rotary drum folders appeared to solve both problems. The cross-folder operated with a 2.4 metre length between folds compared with 1.2 m for the swivel arm and 0.9m for the rotary folder. This roughly doubled the length per pack and halved the number of folds. Despite the apparent additional mechanical complexity, Mr Rahn claimed no higher investment (in €/m 2 /year) than required for the swivel arm system, but stressed that the equipment would vary widely depending on the precise range of products it had to handle.

For the future he saw the KorTec system being able to plait product directly into a container (did he mean a shipping container?), and the possibility of cores being delivered pre-cut to diaper size in special dispensers. Spooling was, he thought, poor in comparison to festooning and would decline.

Through-Air Drying

J.A.Villalobos (Air-Therm Corp.) related the problems he had encountered starting up the first commercial air-lay machines:
• Latex bonded fluff pulp has zero strength, so the transfer from the forming wire into the dryer was very troublesome.
• Flat-bed driers with low air pressure above the bed were essential.
• Dust in the recirculated air was a real problem because it discoloured and filtered out on the surface of the web.
• Honshu filtered all the air fed to the dryer to solve this problem, others used 100% fresh air with heat recovery.
• Heat exchangers (used for heat recovery) condensed plasticisers from the latex and clogged with dust. (Prone to fires.)
• Synthetic (as opposed to metal) dryer conveyors were preferred, with dryers being longer and cooler than might be expected. (low temperatures minimised dust discoloration)
• Air distribution and temperature control across the web were crucial. Closely spaced free-wheeling rollers under the conveyor created narrow distribution slots continuously cleaned by the slightly faster moving conveyor.
• Baffles above the bed formed matching slots.
• Baffles were usable below the bed, saving some roller costs, where the fabric was reasonably well bonded.
• Air temperature uniformity requires the use of line-burners - to release heat over a larger area - and air-mixers before the hot air enters the dryer.
• The key learning: It's cheaper to spend money at the beginning than to patch up the problems later.

Ultra-Low Melt Bico

Ida Pittman (KoSa) covered the use of a lower, broader melting range polyethylene obtained from Dow's constrained geometry catalyst process. She compared a bicomponent fiber with this new polymer as a skin on a polyester core (“LM”), with their popular T255 bico that has a similar core with an ordinary polyethylene skin:
• Fiber tensile properties were similar.
• The LM surface melts at 108 0 C – giving a bonding window 20-30 0 C lower than T255
• It flows faster and recrystallises at 91 0 C, giving lower dusting levels and higher strength.
• Like T255 it still requires an adhesion promoter for best bonding to pulp. (2 den 6mm LM with adhesion promoter gives 1600 g/in CD strength compared with 250 g/in for LM alone - 12% of fiber added to pulp in a 173 gsm airlaid bonded at 140 0 C.)
• Dry and wet CD strengths for LM were almost double those for T255 (conditions as above)

In response to questions Ms Pittman said the LM fiber was sold at a premium. It would find application in the processing of heat sensitive materials or when bonding needed to occur during a drying operation. She thought the fiber would also find application in calendaring processes. She could not reveal the adhesion promoters used.

High SAP Pre-formed Cores

Mark Bolyen (MTS Inc) reviewed data on airlaid diaper cores first given at the Aarhus NTC in 1999 adding new information on MTS's work with lighter weight structures. Here the thinking seemed to be to make a much thinner (100gsm) core, highly loaded with SAP and surfaced with a low-density bico acquisition layer to help contain the SAP and increase its strength. Multiple layers of this tested as a diaper core did not perform well because the SAP-containing part of the core would not pass fluid into the ADL below it. Wider widths of the composite could however be “ZS” folded in-line to give an effective 300gsm three-layer core. Such use of multiple layers of lighter webs would, Mr Bolyen thought allow much longer run times (more metres on any given spool or “brick”).

Some core-comments:
• Thermal bonding of cores does reduce their absorbency.
• Densification increases vertical wicking but reduces capacity and acquisition rate.
• Tissue/SAP laminates and SAP fiber/Bico composites gave the highest SAP concentrations in structures that worked, but these were too expensive.

Wet-Laid/Airlaid Combinations

Jim Hanson (MTS Inc) revisited the case for adding an air-lay former to a board machine to increase throughput and save energy in the container-board market. This time test data on the properties of various laminates made from ~200gsm of wet-laid northern softwood kraft at 25% moisture with 200 gsm of unspecified airlaid were provided. The laminates had been made at various laminating pressures in a slow calendering operation at 400 0 C.

The presence of airlaid generally increased the thickness but reduced the tensiles and burst strengths. Interestingly, and here mimicking the performance of some advanced composites, the product with an airlaid layer between two wet-laids more than doubled the Tabor stiffness compared with the results from 2 layers of wet-laid alone.

INDEX 02: Geneva - 16-19th April 2002

Highlights 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 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 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 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 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%. 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