Thursday, 16 November 2000

Crop-Based Polymers for Nonwovens


The imminent large-scale production of biodegradable polyesters from corn-starch will give nature's most abundant polymer, cellulose, increasing competition in the nonwovens industry. Is a further decline in the use of cellulose in nonwovens inevitable or could interest in the new "nature-based" fibres and plastics enhance the prospects for all crop-based materials? How will the costs of the two approaches compare? Will the absorbency advantage of cellulose prevail over the thermoplasticity advantage of polylactic acid. This paper compares and contrasts the two main "natural" routes to polymers and the properties of the resulting fibres.

Introduction: The PLA Investment

The US no longer has abundant oil reserves but does have a super-abundance of agricultural resources capable, given appropriate levels of chemical (fertiliser/pesticide) input, of annual regeneration. The US currently imports 50% of its domestic petroleum consumption, yet exports 20% of its grain production. The production of ethanol from grain was an early example of an attempt to better balance this resource budget, and the current PLA project appears to be part of a similar but separate program with the objective of allowing agriculture to provide 10% of the US chemical industry building blocks by 2020 and 50% by 2050. The program, called the Plant/Crop-based Renewable Resources Vision at the US Department of Energy has had the full support and co-funding of the National Corn-Growers of America since 1997. The resulting “Renewable Resources 2020” is a broad-based coalition of agricultural, forestry, and chemical industry experts working to create plant-based replacements for fossil-fuels.

The NCGA commenced funding of PLA research in 1994 while working with Cargill to help them seek funding through US Department of Commerce grants. Cargill first joined forces with Purac Biochem BV to perfect the fermentation step and then with Dow in 1997 to build the first pilot-plant. At that stage they projected large-scale production in 2001 to give a PLA polymer at “around 50 cents/lb”. This first 140,000 tonne/year Blair PLA plant would cost $300M and consume 14 million bushels of corn per year, but to the NCGA, the market potential for PLA would be 500 million bushels per year of corn - almost as much as the current usage in ethanol production - estimated to add 25 cents per bushel to the price of corn.

The technological vision was bold and clear, and maybe as a natural consequence, the marketing vision is now broad and evolving. Early announcements said PLA would be the first renewable resource to stand alone on price and performance in applications such as fabrics for clothing, plastics for cups, food containers, packaging, and home/office furnishing such as carpets.

Cargill-Dow Polymers LLC, (the 50/50 joint venture between Cargill Inc and The Dow Chemical company formed in 1997), has, in a series of announcements this year, made it clear they believe crop-based biodegradable fibres to have a bright future in comparison with the fossil-fuelled synthetics. Blair, now due to commence production of PLA in early 2002, was chosen because of its proximity to the lowest cost source of the dextrose sugar from which the PLA is made - a large Cargill wet-milling plant - thereby allowing it to achieve the best possible supply chain costs. The earlier JV between Cargill and Purac Biochem BV brought a 34,000 tonne per year plant on stream, also at Blair in 1998, to manufacture lactic acid from dextrose. This feeds, amongst other end-uses, the 4000 tpa Dow PLA pilot plant in Savage MN.

A biodegradable polyester with the cost and easy-care properties of real polyester, yet based on renewable resources rather than oil is clearly an unmet need. It should be highly saleable in both woven and nonwoven products as well as in many types of plastic containers. While the publicly available information makes it clear that conventional polyester, polystyrene and polypropylene are major targets for this new crop-based polymer, comparisons with the old biodegradable crop-based polymer, cellulose, are largely absent. PLA fibre is said to “bridge the gap” between natural polymers and the synthetics, offering a unique combination of properties combining the best attributes of natural and synthetic fibres. It’s positioning, in a world where the synthetics continue to displace the natural polymers on cost/performance grounds, is excellent. Most people are vaguely concerned that the plastics are in some way bad for the environment, but, in the mass market at least, have not been concerned enough to pay more for less convenient natural products.

Polylactic Acid Development

Polylactic acid was first made in 1932 by Carothers, who developed a process involving the direct condensation polymerisation of lactic acid in solvents under high vacuum. He abandoned the polymer as too low in melting point for fibres and textiles and went on to develop nylon.

More recently PLA was developed as an alternative binder for cellulosic nonwovens because of its easy hydrolytic degradability compared with polyvinyl acetate or ethylene-acrylic acid copolymers.

Spunlaid and meltblown nonwovens based on PLA were researched at the University of Tennessee Knoxville in 1993.

Kanebo ( Japan) introduced LACTRON® (poly L-Lactide) fibre and spun-laid nonwovens in 1994 claiming a capacity of 2000 tpa being expanded to 3000 tpa. It targeted agricultural applications to start with, and in 1998 was re-launched for apparel end-uses. At that time, Japanese demand for PLA fibres was said to be 500-1000 tpa. In order to improve the biodegradability and reduce the costs of the nonwovens, blends with rayon were also developed.

Fiberweb (now BBA, France) disclosed nonwoven webs and laminates made of 100% PLA in 1997 and introduced a range of melt-blown and spunlaid PLA fabrics under the Deposa™ brandname. The polymer was developed by Neste Oy.

Galactic Laboratories ( Belgium) provided an excellent overview of polylactic acid polymers, concluding that 390,000 tonnes of the polymer would be produced by 2008 at prices around $2/kg. Their estimate of 70,000 tonnes for 2002 looks about right with the new Cargill-Dow plant due to start during that year. It remains to be seen if the price will be right also.

And this year, Cargill Dow Polymers LLC, as mentioned in the introduction plan to double their 4000 tpa capacity for the polymer EcoPLA™, now rebranded NatureWorks™ “to meet immediate market development needs". In January they also announced the construction of the Blair plant to make "a family of polymers derived entirely from annually renewable resources with the cost performance necessary to compete with traditional fibres and packaging materials". Fibre Innovation Technologies, Parkdale, Unifi, Interface, Woolmark, Unitika, Kanebo and Kuraray are mentioned as Development Allies.

Several other producers are still active. At Index 99, NKK ( Japan) showed a PLA spunbond nonwoven at 15gsm with apparently excellent formation and properties, although they later admitted that this was to demonstrate the flexibility of their spunbond machinery, and not a commercial product. Kuraray ( Japan) showed PLA fibres and provided some data on their properties and biodegradation rates. PLA polymer is made in Japan by Toyobo, Dai-Nippon Ink Chemicals, Showa Polymers, Shimadzu Corp and Mitsui Toatsu , the latter under the LACEA™ brandname. Unlike CDP, MT’s process polymerises the lactic acid direct from the monomer), At Anex 2000 in Osaka, Shinwa were showing a PLA version of their Haibon® spunbond: “a natural biodegradable nonwoven”. Kanebo again promoted their Lactron® fibre, but this time based on the CDP polymer.

The PLA Fibre Process

The CDP process, involves extracting sugars (mainly dextrose, but also saccharose) from cornstarch, sugar beet or wheat starch and then fermenting it to lactic acid. The lactic acid is converted into the dimer or lactide which is purified and polymerised (ring-opening method) to polylactic acid without the need for solvents . The family of polymers arises in part from the stereochemistry of lactic acid and its dimer. As fermented, lactic acid is 99.5% L-isomer and 0.5% D-isomer.

Conversion of this lactic acid to the dimer can be controlled to give three forms, the L, D, and Meso lactides.

Polymerisation of the lactide to give polymers rich in the L-form gives crystalline products, whereas those rich in the D-form (>15%) are more amorphous. The enhanced control of the stereochemistry achieved in the dimer route accounts for the superiority of the current products over those from the 1932 Carothers approach.

In block diagram form the PLA production sequence is:

Seeds, Soil, Water, Carbon dioxide, Sunlight 

Biomass, ideally corn 
Harvest/Wet Mill
Acid/Enzyme Hydrolysis
Lactic Acid 
Crude Polylactic Acid Pre-polymer 
Crude Lactide monomer 
Fractional Distillation
Pure lactide monomers 
Polylactic Acids 
Modification for end-use
Granules for extrusion etc. 
Melt Spinning
“Crop-Based” Polyester Fibres

Producing the lactide with the right purity and stereochemistry to make decent fibres is not trivial. In a recent Cargill patent, the refining process, intended to be able to cope with crude lactic acid feedstock, was illustrated as follows:

Feed Crude Lactic Acid to Evaporator continuously
Remove water or solvent 
→ discard or recycle water, solvent or by-products

Feed concentrated lactic acid to a pre-polymer reactor

Polymerize to form pre-polymer by removing water → discard or recycle water, solvent or by-products contaminated with lactic acid

Feed in catalyst→ Feed pre-polymer to lactide reactor→Remove high-boiling unreacted polymer

Remove crude lactide as vapour↓Partially condense crude lactide →Remove lactide impurity as a vapour

Purify crude lactide in a distillation column →Remove lactide impurities

Remove purified lactide as high-boiling bottoms from the column


Before examining the claims for PLA fibres in comparison with other crop-based polymers, we should refresh our memories with a review of the routes to other crop-based polymers in the form of cotton and rayon fibres:

Rayon in similar block diagram form would be:

Seeds, Soil, Water, Carbon dioxide, Sunlight
Wood Pulp 
Cellulose Solution 
Impure fibre 
Pure Wet Fibre 
Bales of Lyocell or Viscose

Cotton in similar block diagram form would be:

Seeds, Soil, Water, Carbon dioxide, Sunlight 
Grow- months
Cotton bolls 
Raw Cotton Bales

This is clearly the simplest route to crop-based polymers for fibre end-uses. However for many of these end-uses the raw cotton has to be bleached to remove the waxy substances that prevent it from being absorbent. This is done either in fibre form for waddings and nonwovens or in fabric form for apparel:

Raw Cotton Bales/Fabrics
Impure fibre/Fabrics 

Pure Wet Fibre/Fabrics 

Bleached Cotton Bales/Fabrics

PLA Claims , and Comparisons with Cellulose

Fibres from the first mentioned EcoPLA™ polymer were said to be:
  • Reminiscent of PET or PS in some forms and of PP and PE in others. 
  • Capable of giving fabrics with the feel of silk and the durability of polyester. 
  • Fully biodegradable under composting conditions. 
  • Convertible into nonwovens by dry- air- wet- spunmelt- laying systems. 
  • Capable of giving improved resilience, moisture transport, breathability and wet strength. 
  • The price was, in 1998, said to be $3-6/kg, but capable of reduction to $1.1/kg at full-scale production. 

Additional claims for NatureWorks™ recently announced were:
  • Value-added natural-based fibres. 
  • Bridges the gap between silk, wool, cotton and the synthetics 
  • Superior handle and touch 
  • "The comfort of natural fibres with the performance of synthetics" 
  • Controlled degradability, enhanced wicking, low linting. 
  • Excellent UV resistance and elastic recovery. 
  • Reduced flammability with low smoke and heat generation 
Nonwoven applications were listed: fibrefill, crop covers, geotextiles, wipes, hygiene, medical, diapers and binder fibres.

Fibre Properties

On the information currently available, PLA looks like an excellent fibre with the right technical credentials to replace polypropylene, and maybe some polyester in nonwovens. As noted by Carothers, the melting point still appears too low for it to challenge the supremacy of aromatic polyester in mainstream textiles. Furthermore the hydrolytic stability under conditions close to some laundering, dyeing and finishing processes is borderline. 

Nevertheless, PLA marketing now seems to be concentrating first on higher value textile applications, and it's biodegradability is not featuring so prominently. There are some interesting parallels with lyocell market development here, lyocell’s fibrillation initially being seen as a problem in dyeing, finishing and laundering but an advantage in nonwovens. PLA’s solubility in alkali could yet turn out to be a major selling point in applications not yet thought of.

The fact that PLA has a melting point at all is, in comparison with cellulose, a fundamentally important advantage in fibre manufacture and disposable nonwoven processes. In durable products, its resilience and abrasion resistance will be equally important. On the other hand, while PLA is more wettable than PET, it does not absorb useful amounts of water.

The recent claims to a 210 oC MPt PLA require a 50/50 melt-blend of pure D- and L- lactides which crystallize with their helical structures interlocking. This technique, first described by Dupont, has yet to be made on a commercial scale.


Unlike cellulose, PLA is largely resistant to attack by microorganisms in soil or sewage under ambient conditions. The polymer must first be hydrolysed at elevated temperatures to reduce the molecular weight before biodegradation can commence. Claims of biodegradability can therefore only be made where a composting infrastructure exists. Data from CDP shows that composting at 60oC causes hydrolytic degradation, which over 10 days depolymerises and embrittles the polymer sufficiently for it to fragment. Complete biodegradation to CO2 occurs over the next 30-40 days.

Cellulose fibres degrade more rapidly and also degrade under ambient conditions when buried in topsoil or in sewage processing. Cotton and rayon are similar.

CDP pledges to support the development of composting infrastructure in those countries (e.g.USA) that don’t have one. However over the last 12 months, the marketing emphasis seems to have changed in favour of durable products; the biodegradability of the fibre getting fewer mentions.


PLA burns like cellulose to yield 8400 Btu/lb energy.

Fossil Fuel Usage

The CDP-PLA process is said to use 20-40% less fossil fuel than fossil-fuel-based polymers. This appears to be less than the saving to be expected from obtaining the monomer from something other than fossil-fuel and CDP admit that the process currently uses more conversion energy than conventional polyester manufacture. In the CIRFS ecoprofiles study, polyester was estimated to use 80 MJ/kg of fossil-fuel energy per tonne of fibre compared with 54 MJ/kg for for viscose fibre. CDP recently 13 quoted 57 MJ/kg for PLA fibre and pledged to reduce this to 34 MJ/kg and then 5 MJ/kg by adopting alternative energy sources in future plants. (Of course any fibre or polymer plant could choose to switch from fossil-fuel and achieve similar reductions, at a price.)

Reduced Global warming

This is due to the corn absorbing CO2 during growth. The CO 2 is released back to the atmosphere on degradation, so over the full life-cycle, “CO 2 neutral” may be a more accurate claim. Trees do the same, and any process based on fresh biomass will show an advantage over those based on pre-historic biomass.

Land/Chemical Usage

PLA requires 3100 m 2 land per tonne of fibre 7. US corn production used about 260kgs of fertilizer/Ha in 1996 equivalent to 840 kgs fertilizer per tonne of PLA fibre.
  • Rayon (South African forests) requires 3000 m 2 land per tonne of fibre. 
  • Rayon (European forests) requires 8000 m 2 land per tonne of fibre. 
  • Cotton ( Texas) requires about 20,000 m 2 land per tonne of fibre 
  • Cotton (California 17) requires 8,000 m 2 land per tonne of fibre 
  • Cotton (World Average 17) requires 15,384m 2 per tonne of fibre 
  • Cotton requires 700-1100 kg fertilizers/tonne fibre 16, along with herbicides, insecticides, fungicides, plant growth regulators, and harvest aid chemicals (defoliants). The land has to be of good quality, well irrigated and could be used for food. 
  • Trees can be grown with no irrigation or chemical inputs on land unsuitable for food crops. 

Post consumer recycling

PLA can be hydrolysed back to lactic acid and repolymerised, the economics of such a process being dependent on the price of fresh lactide. There is no equivalent economic route for cellulose, except via the atmosphere.
Other issues

CDP pledges to address other environmental issues related to the PLA process:

  • They will encourage the use of variable rate fertiliser technology to reduce farming emissions. 
  • They will try to develop processes to use non-food agricultural sources of dextrose. 
  • They will address the Genetically Modified corn issue. (Cotton has similar problems with GM varieties being mixed with non-GM. Some consumer organisations are concerned by the resulting inability to choose GM-free products. The trees used for rayon production have not been genetically modified.) 

Pollution from manufacturing processes

In life-cycle inventory terms, a comparison of the effluents from the PLA route with those from the viscose and lyocell routes is clearly important, and is an area where PLA should show an advantage. CDP has already made the Life Cycle Inventory for the Blair plant available to customers and pledged to make it available to the public. At the time of writing it had not been received. A few general observations may however be helpful.

Wood pulping and corn processing have similar problems of separating biomass into a variety of useful materials. Corn processing appears to have a clear advantage because milder treatments can effect the necessary separations, and the majority of its constituents have economic value. Starch processing and fermentation are well-understood processes whereas wood chemistry is much more complex. Separating cellulose from lignin is difficult and today’s processes use aggressive chemicals and produce effluent that is hard to deal with. Furthermore the second most important constituent of wood, the lignin currently has little or no economic value due to the low value placed on fossil reserves.

Technology already exists to allow most of the constituents of wood to be harvested with much reduced environmental impact, and the US Department of Energy are funding several schemes. The fossil-fuel price increases needed to accelerate the development of PLA will also accelerate the investments in these new wood-processing plants.

PLA, like polyester, is likely to remain ahead of cellulose when the effluents from fibre manufacture are considered. While lyocell is a great improvement on viscose, it has to be regenerated in water and will always need washing and drying.

Economic Factors

The production of dextrose and lactic acid from biomass is well established and already a major industry. Lactic acid for polyester manufacture has to compete with the other uses of dextrose, such as sweeteners, and as a precursor for ethanol, citric acid and vitamin C. Similarly, the lactide route to polyester has to compete with the other established uses of lactic acid, in food additives, solvents, pharmaceuticals, emulsifiers, chelating agents, cosmetics, propylene glycol, methyl ethyl acrylate, and several fine chemicals.

Worldwide consumption of lactic acid was between 130,000 and 150,000 tonnes in 1999, about half being used in foodstuffs. Plastics, emulsifiers, pharmaceuticals and cosmetics accounted for about 10%-15% each. Food grade material, unsuitable for plastics or fibres cost about 90c/lb in the USA or 65 c/lb in Europe where Chinese material had depressed prices. The cost of the purer lactic acid needed for PLA production was estimated to be $2-3/lb. Annual lactic acid market growth was put at 15% per year.

PLA polymer currently costs around $5/kg and as mentioned earlier, is expected to fall to around $2/kg when production reaches 390,000 tonnes/year, estimated to be in 2008. If it converts to fibre with the efficiency of a regular polyester resin, the staple fibre price could be as low as $2.4/kg. At today’s prices, this would put it on a par with those other crop-based polymers, bleached cotton, viscose rayon and lyocell: i.e. about twice the price of the fossil-fuelled synthetics.

CDP has suggested $1.1-$2.2/kg for the resin from the Blair plant in 2002, although more recently has indicated $1.1/kg will only be possible when cheaper waste biomass can be processed into dextrose. This could not easily be done in the Blair location.


This is an interim report of an ongoing study and any conclusions must be provisional and rather subjective. The promised life cycle inventory on CDP’s PLA process remains to be published and may well contain information that invalidates some of the thinking here. The following observations are nevertheless offered to summarise the work so far:
  • Pre-historic biomass, on which the 20 th century industrial economy was founded, will, in this century, lose its pre-eminent position as a source of chemical building blocks to freshly grown biomass. 
  • Three major components of fresh biomass, cellulose, lignin and carbohydrates are between them capable of providing precursors for plastics, fibres, fuels and chemicals and will do so increasingly as the price of fossil-fuel increases. 
  • Cellulose is not only the most abundant polymer in biomass. It grows as fibres e.g cotton, linen, hemp, kenaf, ramie etc., or as wood that can be converted into fibres by purification, dissolution and reprecipitation. 
  • Carbohydrates in agricultural crops can be degraded to sugars, fermented to lactic acid and repolymerised to make, amongst other things, a synthetic aliphatic polyester, eg CDP PLA. (Some plants and bacteria synthesise polyesters directly and other biomass utilisation projects are based on their optimisation and extraction). 
  • Wood processing technology currently concentrates on extracting the cellulose, and generally burns (to reduce fossil fuel usage) or rejects as effluents other potentially valuable materials. 
  • Corn processing technology already separates corn into many edible materials, some of which are converted into monomers from which polymers can be made. 
  • PLA resin and dissolving pulp are both nature-based polymers ready for use in fibre forming processes; pulp having the more direct connection with natural processes. 
  • PLA is easily and cleanly convertible into fibres using melt-spinning technology, whereas converting woodpulp to fibre is more complex, uses more energy and for the viscose route at least, produces more effluent. 
  • PLA claims environmental advantages over PET due to its reduced use of fossil reserves, it’s compostability, and its production, albeit indirectly, from an agricultural product. 
  • Cellulose has environmental advantages over PLA due to being present in nature as a fibre-forming polymer, being easily biodegradable in all processes and (in the case of rayon) using less fossil reserves, fertilisers, pesticides, and agricultural land than PLA. 
  • Cellulose in the form of cotton uses least fossil-fuel, but its low cost is due to high yields per hectare achieved by the intensive use of water, pesticides, fertilisers and defoliants. 
  • While not a current problem for US agriculture, farmland will become increasingly needed for food production. 
  • In many textile applications, polyester/cellulose blends provide an ideal combination of durability, easy care, texture and comfort. The current low-melting point aside, PLA would be equally good. 
  • In nonwoven applications, PLA being more wettable than polyester or polypropylene could make an excellent coverstock or acquisition layer fibre. Cellulose is not only wettable, but highly absorbent in comparison. 
  • PLA binders could latex-bond cellulosics: PLA fibres could thermally bond cellulosics. 

And Finally…

  • The US Department of Agriculture is backing research into both corn and wood based routes to renewable energy and materials. 
  • Corn and PLA are currently centre-stage thanks to the publicity surrounding the CDP Blair investment, but forestry and cellulose, despite a poor image related to past pulp and paper production methods, can also yield fibres, and chemicals -including PLA. 
  • PLA has all the strength and processing advantages of a thermoplastic synthetic fibre: the higher melting point versions being technically capable of replacing polyester. 
  • Polyester/cotton has been the most successful textile blend of the 20 th Century: High Melting PLA/lyocell blends could replace it with significant environmental advantages. 
  • The rate of development of nonwoven products based on PLA, will, like the development of nonwovens based on lyocell, depend on the relative attractiveness of textile and nonwoven applications to the fibre producers.

Copyright: Calvin Woodings Consulting Ltd. 2000


“Corn and Agricultural Vision: Renewable Chemical Building Blocks for the Future” - PR Newswire, April 19 th 2000

“Dow and Cargill in Joint Venture for New Resins”, Financial Times, 25 Nov 1997

Bonsignore PV et al, "Polylactic acid degradable plastics, coatings and binders" TAPPI Nonwovens Conference, Marco Island, 1992

Wadsworth L et al, "Melt processing of PLA resin into nonwovens", 3 rd Annual TANDEC Conference, Knoxville, 1993.

US Patent 5,702,826, Ehret P et al, Dec 30 th 1997, assigned to Fiberweb.

P Ehret, "Deposa Nonwovens: Deposable disposables" INSIGHT 96 San Antonio.

Bogaert and Coszach, "Polylactic Acids: New polymers for novel applications" Speciality Polymers Session, INDEX99 Geneva.

The Dow Chemical Company, Press Release 11/1/2000.

Lunt J, Shafer, A, "Polylactic Acid Polymers from Corn: Potential Applications in the Textile Industry", Cargill Dow Polymers LLC,

Lunt, J; “Polylactic Acid Polymers: Technology and Applications for the Fiber Industry”, Nonwovens Network Seminar, Wakefield, June 2000.

USP 6,005,067 (Dec 21 st 1999) to Cargill Inc

CDP Product information - Jan 2000

“Polylactide Polymers: Technology and Applications”, Lunt, J, CDP LLC, paper at INTC 2000, Dallas, September 27 th 2000

“Ecoprofiles of Selected Man-Made Fibres”, CIRFS (The international committee for rayon and synthetic fibres) Dec 1997.

SAPPI - Private Communication

“Clean Production of Rayon- An Eco-Inventory” Josef Schmidtbauer, Lenzinger Berichte No. 76, 1997

Spaar T, MSc Thesis, Environmental Science, Swiss Federal Institute ofTechnology, Zurich.

“Lactic Acid Prices Falter as Competition Toughens”, Chemical Market Reporter, 1 March 1999

Thursday, 9 November 2000

Insight 2000: Toronto, 30th Oct to 2nd Nov

Toronto and Royal York Hotel

Global hygiene market statistics

John Starr estimated the Global hygiene absorbent products market to be worth $40b in 1999. Disposables had now penetrated about 15% of the total available market, or 41% of the “major” markets. Diapers and training pants amounted to $19b or 84 billion units; $16b or 160 billion units were tampons, sanitary napkins and panty-liners (the tampons accounting for 16 billion units) and there were 12 billion ($5b-worth) adult incontinence products. The industry consumed 36 billion sq.meters of coverstock, 3.3 million tonnes of pulp, 1.1 million tonnes of SAP and 500,000 tonnes of barrier film. 40% of a diaper makers total manufacturing revenue is spent on raw materials.

Use of spun-melt fabrics , 825,000 tonnes in 1999, continues to grow at 8-9% per annum. The newest lines are flat-out, but some under-utilised capacity exists among the older systems. Further capacity expansions would be needed by 2003, each new line adding 15-20,000 tonnes of output. Carded thermal-bonded products were mainly PP (300,000 tonnes) but 50,000 tonnes of PET were also used. New very-fast card lines (~ 400m/min) were being installed in Europe to meet the increasing demands for AD layers and textile-like backsheets especially from Procter and Gamble. SAP capacity is expected to reach 1.4 million tonnes by 2003, the profitability of this business being dependent on capital and acrylic acid costs: 1999 operating profit was put at 16 to 22%. Fluff pulp usage per unit continues to decline, but total tonnage could continue to increase for several more years. Pulp profitability depends crucially on the pulp-price which has varied from $550 to $850/tonne in recent years (now around $700/t c.f. $550/t during 99). Air-laid core usage is expected to reach 190,000 tonnes by mid-decade, but if a major new diaper uses a preformed air-laid core, i.e. if the cost and high-speed delivery problems of this approach are solved, this could rise to 260,000 tonnes. For the future, improved fit arising from the use of elastic fabrics and renewed (but cost-effective) attention to consumers environmental concerns could be expected.

Fiber supply, demand and trends

Dick Osman of Kosa reviewed fibre supply and demand using Fibre Economics Bureau and PCI statistics. Total world usage was now 60 million tonnes and had grown at 2.5% per year but for oil-crisis hiccups. The 1999 figure was unusually high because 4 million tonnes of “other natural fibres” such as jute, hemp and ramie had been added to the data for the first time. Population growth was put at 1.7 % per year globally, and per capita consumption growth at 1.25% per year. World average per capita consumption was 8.3 kg/person, with the USA using 35.8 kg/person. 32% of the total usage was cotton, but polyester (30%) was growing much faster and would overtake cotton this year. PP had 9% and regenerated cellulosics 4%. Cotton production appeared to have peaked with acreage and yield/acre being similar to the mid-eighties level. In contrast, polyester filament was expected to grow to 8%/year to 2005, and staple at 6%/year. Capacity utilisation would improve from 82% in ‘98 to 88% in '05 for polyester staple and from 74% to 80% for filament. For the future the new fibres to watch were PTT, a nylon-like polyester now being made at lower costs due to a production technology breakthrough at Shell, and polylactic acid. Bicomponent fibers would continue to grow, the technology being adapted to allow exotic, expensive or even non-fibre forming polymers to be carried into fibres by regular polyester and polypropylene.

Air-Laid Markets; Wet Wipes

Susan Stansbury of Fort James Nonwovens pointed out that despite all the interest in thermal and multi-bonding air-laid production, more than 85% of air-laid pulp products were still latex bonded. Air-laid consumption by market was 24% in femcare, 20% in wet-wipes, 18% in dry-wipes, 15% in table-linen, and 5% each in adult incontinence and medical products. 13% remained undefined. Use in industrial wiping is expected to grow as the EPA recognises the hazards of reusing cloth wipes contaminated with solvent. New regulations favouring disposables are expected to be on the Federal Register early next year. In the consumer market, the bulk and embossability of air-laid was felt to be a major advantage over the more expensive hydroentangled products, but a detailed comparison based on specially commissioned consumer research was of limited value because the hydroentangled control was a wet-laid product (Dexter's Hydraspun®). Against this material the Fort James baby wipe products performed best in all measured attributes. Air-laid wipes dominated at the low end of the market and competed successfully with wet-laid at the higher intermediate level. However, for premium wipes air-laid could not match the dry-laid hydroentangled materials. In response to questions Ms Stansbury said FJ was also operating multibonding air-lay systems in both Europe and the USA , and was developing another unspecified binder technology. Air-laid continues to grow at rates in excess of 10% per year. Antimicrobial additives do work in dry-wipes, provided the wipe is wetted before use.

Air-Laid Update

Ivan Pivko's update of air-laid developments referred to BBA's installation of a new line in China , Concert's two new lines going into Quebec and Buckeye's really big line now being built in North Carolina . He felt the expansion was being led by Procter and Gamble, J&J and Kimberly Clark who, despite industry concern about the solidity of their commitment to air-laid diaper cores, really would absorb the output of these investments. With regard to the use of air-laid in wipes, Mr Pivko felt air-layers had limited interest in this market. Wipe producers had little loyalty to any particular air-laid product, regarding them as commodities to be bought at the lowest possible price. Air laid producers would in turn regard the wipes market as a capacity filler. For the future he recommended watching developments from Woodbridge Foam, JATI (the “Megathin” diaper cores based on 80% powdered SAP and microfibres) and Procter and Gamble's superthin core based on a “mixed-bed ion-exchange superabsorbent polymer composite with very little pulp” (USP 6121509).

Advanced Air-Lay Laminates

Phil Mango of Concert Inc. had sampled 40 commercial baby wipe products finding 15 hydroentangled fabrics, 11 air-laid, 5 composites, 4 carded, 3 meltblown, 1 Coform™ and 1 wet-laid. He then ranked each type for strength, linting, softness, bulk, liquid dispensing, and cost, finding that hydroentangled fabrics were best for strength, linting and softness while the air-laid approach gave the best bulk, liquid dispensing and cost. He went on to postulate the need for an advanced air-lay system capable of giving the best of both worlds by combining air-laid pulp and man-made fibres with pre-formed HE fabrics, scrims, films both plain and perforated, spunmelts, powders, liquids and latex binders to produce composites with at least 3 layers and even more components. His “better baby wipe” had essentially 5-layers, a central film, pulp/bico airlaid either side, the surfaces being skinned with latex. His “Ultimate Bathroom Cleaner” used a spunbond polyester, latex-bonded to a pulp-bico air-laid, the other surface being covered with an antimicrobial, non-ionic, spray-applied latex. The “Medicinal Dispensing Pad” was similar with film replacing the latex back. In response to questions, Mr Mango thought a 60 gsm sandwich of 13gsm PP spunbond either side of airlaid pulp would be cheaper than a 60gsm PET/Viscose HE fabric, and that this approach to strengthening airlaid pulp would prove to be better than adding bico fibres. The incorporation of microencapsulated liquids could be foreseen to allow two dissimilar liquids to be mixed at the point of use. The use of polyvinyl alcohol binders would allow the production of flushable air-laids.

Air Lay Plant Developments

Henning Skov Jensen of M&J Fibretech a/s ( Denmark ) introduced two new developments while revisiting their proposals of the last few years, i.e. the 5-layer air-laid diaper core, the Super-Site concept and the super high capacity diaper core line. The first new development was air laying an 8gsm 70%cotton-linter/30% bico layer on a 10gsm SMMS fabric to form a “nit-free cotton linter breathable backsheet”. The second was a binderless diaper core where longer than normal cellulosic fibres including hemp and flax are laid and compressed to make a hydrogen-bonded all-natural absorbent pad at about 0.4gms/cc density. Both of these were being patented.

The output figures for the diaper core line had been revised upwards since last year. A 10 row 90 paddle forming head (or two 5 row heads) allowed the laying of 2.5 tons/metre width/hour of 50/50 pulp/SAP diaper core. If five 5-row heads at 5 m width were run at the very practical 200 m/min speed, 200,000 tons of production could be obtained from a single line. Feasibility cost calculations for the 5-layer composite were however based on 102,000 tons/year output. The line would cost $46m (c.f. $58m for 90,000 tonnes output in last years study) Fluff pulp was at $750/ton (c.f. $550/ton last year), total investment costs were $7m/year (c.f. $8.6m/year last year) and the total cost of saleable diaper core on jumbo rolls was $1981/ton including acquisition and distribution layers but excluding overheads, working capital, rewind slitting festooning and converting. Last year's figure of $1704/ton was based on a multibonded fluff/SAP core only. Also of interest: PP/PE bico fibre was listed at $1800/ton this year c.f. $2850/ton last year. Superabsorbent fibres were included in this years costing at $4400/ton.

Air-Laying man-made fibres

Jim Hanson thought pulp air-layers could be used to outperform cards in the preparation of random webs of 100% man-made fibres. (High speed processing of 100% polyester short-cut had been demonstrated at IDEA 98 on the DanWeb pilot line installed at the exhibition.) Air-lay production speeds of 350-450 m/min were possible now, 600 m/min was just around the corner and 1000m/min was likely to be reached in 2 years. Using the MTS DanWeb pilot line, web-weights as low as 2gsm had been made from 1.7/6mm bicomponent fibres and samples of 6mm Tencel 60/40 with bico at 7 and 14 gsm were also shown. In a related development, 92% granular SAP had been formed into a sheet with just 8% of bico, all of the above being achieved using fibres optimised for carding and air-layers optimised for pulp. Bicos had been totally split into microfibres by the DanWeb head on pulp settings. Clearly the use of fibres longer than about 12mm will always be difficult through screens, but then carding will never match the air-layer's ability to run fast and light.

Air-laying card webs

Air-laying of long fibres at higher speeds will be possible using a new Turbo unit from Spinnbau Bremen . Siegried Bernhardt described how they had taken over the Hergerth-Hollingsworth concept of roller-train card followed by a Turbo air-layer in 1996 and further developed it into the current patented system. This new system has the potential to handle 360-400 kgs/hour/meter width of 1.7 dtex fibre and produce fully randomised 200 gsm webs at 28 m/min or 60gsm webs at 100m/min. The key to productivity with randomness is the amount of fibre you can load onto the cylinder and its surface speed related to the doffing speed (the compaction ratio). In conventional carding, compaction ratios of around 10 are used, but for air-laying they need to be 60 or more. 100m/min output therefore requires a cylinder surface speed of 6000m/min. To get to this from the current 4800m/min maximum, traditional construction methods must be abandoned, but details of how SB would achieve this were not given. By implication, the current theoretical maximum carding speed using steel and aluminium constructions would be 480 m/min and Mr Bernhardt commented that cards were already producing PP coverstocks at 370-380 m/min.

Pulp industry problems

In an extraordinarily frank and heartfelt presentation, Peter Abitz of Georgia Pacific addressed the problems of a fluff-pulp supplier in the age of superabsorbents and, intentionally or otherwise, highlighted the issues natural materials suppliers should have addressed to resist the onslaught of the synthetics in an age of cheap oil. He defined the current purpose of pulp as simply “to provide a porous matrix for suspending and distributing superabsorbent particles” and bemoaned the opportunities lost to pulp through inadequate attention to market trends and customer needs. Fundamentally important benefits such as low (if unstable) price, unbeatable wettability and softness had not been developed, and the pulp industry had simply watched while the superabsorbent producers had “eaten our lunch”. True, the first superabsorbents and even the first acquisition layers for thin diapers had been based on chemically modified pulps but now synthetics had taken over.

Why? On the one hand the diaper producers preferred to add preformed products rather than defibrate another roll of fluff, and on the other hand the pulp industry had decided not to continue with the investments needed to create widespread availability of the modified pulps. Investments in silviculture research continue but Mr Abitz doubted that designer trees with customised fibre properties would appear in our lifetime. Even if they did he felt the anti-GM lobby would probably get them banned from use in diapers. His industry was more interested in growing cheaper and better timber: pulp mills had become the “bottom feeders” of the managed forest, capital intensive, inflexible and therefore unable to adapt to customers evolving needs.

A typical mill such as GP's Brunswick Mill produced 2000 tonnes/day of fluff, employed 800 people ($50m payroll costs per year) and at best made 8% ROC. A new mill would cost $1bn and we would never see another built in the USA . Capital investment was now driven by environmental issues, the US pulp industry expecting to spend $8bn on current mills without payback, even after closing some of the older inefficient mills. The strategy was now to rationalize and decapitalize, to maximize asset values and to try to ensure a 2-way value flow with benefits to the pulp industry and the customers. GP would focus on low capital developments addressing clear market trends e.g. developing easily defibratable pulps suitable for the emerging markets in developing countries. Within all the current constraints Mr Abitz saw the following future possibilities:
• Creating “mild” superabsorbency in a fluffing pulp.
• Utilising longer fibres, maybe even rayon, to improve web integrity. (Reducing SAP powder use would have a bigger effect given a more absorbent pulp.)
• Better wicking from higher density pulp webs in a layered core.
• Additives for odour control
• Creative commercial options to reduce the effects of the pulp-price cycle
• Use of fluff in non-hygiene applications (e.g. sound-proofing)

As an aid to new application development he saw air-laid fluff-pulp as the cellulosic equivalent of spun-laid synthetics and hoped the pulp industry would be able to unlock the value yet to arise from broader use of the air-laying technology.

Fluff pulp debonders

Dr Craig Poffenburger of the Goldschmidt Chemical Corporation estimated the market for fluff-pulp debonders at 3-15 million lbs assuming world production of 3.3 million tons fluff all used the materials. In comparison the US tissue requirement for the related softners and crepe-aids would be 4-10 million lbs, the wide spread reflecting the possible range add-ons. Debonders should ideally be FDA approved, have minimal effects on absorbency, be chloride-free (non-corrosive) and environmentally friendly (no VOC's). Goldschmidt's Arosurf PA 777, based on a imidazolinium methosulphate, claims to be the first debonder to meet all these requirements. It conforms to 21 CFR FDA 176.170 (indirect contact with aqueous and fatty foods) when used at levels below 10lbs per tonne on pulp. Trials at MTS with Rayonier JLD-E debonded with 4.4 lbs/tonne of the PA777 and 2 competitive products showed reduced fluffing energy requirement, comparable absorbent capacity under load but like other quats slightly inferior demand wettability and wicking. To correct this their newly developed Z-Quat™ ester quats incorporate 2 polyethoxylate chains for enhanced hydrophilicity, 2 ester functionalities for improved biodegradability and 3 fatty acid groups for better lubrication and softening. These do not yet have FDA approval. In response to questions, the fatty acids used are of vegetable origin to meet European requirements, but the PA777 does not yet have BGA approval.

High-speed splicing

High-speed conversion of nonwovens runs into splicing difficulties and problems with bearing life and tension control. Jim Ward of Martin Automatic offered their Airnertia Roller™ technology as a possible solution. Here a non-rotating steel core carries a very thin carbon fibre sleeve riding on an air cushion replenished through the steel core. This provides virtually friction-free support for a roll having a fraction of the rotational inertia of conventional systems. In a 120” wide laminating system where web-tension tolerance was 10 to 50lbs and a maximum allowable tension change was 10lbs, the Airnertia Rollers™ allowed a 44% reduction in roll diameter, a 41% reduction in rolling mass and a 369% increase in splicing speed. Much lower overall tensions, even zero tension is achievable with the new rollers.

Shipping air-laid diaper core on roll

A case for making rollers and cores larger in diameter exists when the problems of delivering air-laid core from production units to diaper producers is considered. Michael Robbie of KT Holdings Inc. (who recently sold their Stakpak™ air-laid core packing technology to Buckeye) now feels that big spools (Superspool™) are the answer. Six 2.4 metre diameter rolls, 2.1 meters wide (on T-Rak™ A-frames) would fit into a standard North American trailer. While 300mm cores holding 2.5 tonnes of air-laid would be the norm, an increase to 750mms would significantly reduce web curvature (in traversing) and losses in thickness due to high pressure at the roll centre. Losses in deliverable length using the bigger core were only 8%. A detailed costing of the system showed delivery of 100 million m 2 /year of 120mm wide diaper core for a cost of 5.5 cents/m 2 if operated on-line at the air-laid producer. 1.48 cents of this would be for spooling, 1.74c for shipping, 0.73c for unwinding into the diaper machines and 0.43c for returning the A-frames. 1.13 c/m 2 were “equipment costs” shared between roll-goods maker and diaper producer. 22 spooling stations would be needed on each 2640mm trim-width air-laid line. In this example 7-8 trucks per day would be needed for delivery.

Durables versus disposables

A 1993-94 comparative study of disposable adult diapers, disposable underpads and reusable cloth pads provided a welcome reminder of the fundamental arguments in favour of disposables. The study, carried out by Diane Storer Brown of the Kaiser Permanente Medical Center was a three hospital randomised clinical trial designed to establish the effectiveness of the products in maintaining skin integrity, and their relative cost-effectiveness when considering nursing time, unit cost, numbers required and the costs of changing bed-linen. The trial enrolled 166 patients and lasted for 3 months. The disposables were provided by Professional Medical Product Inc (now TYCO's Kendall Confab Retail Group) in two versions, with and without SAP. The linen underpad had a rubberised backing. Analysis of Variance was used to arrive at the following statistically significant conclusions:
• Skin integrity deteriorated most with the SAP-free products.
• Skin colour change was most severe for the SAP-free diaper followed by the cloth pad.
• Patient complaints of soreness/itching were most severe for the cloth pad.
• SAP-containing underpads affected skin integrity least.
• Product costs per change were least for the SAP-free products.
• Bed-linen laundry costs and staff time costs per change were lower for the cloth underpad and the SAP-containing underpad.
• Overall costs were lowest for the SAP-containing underpad and highest for the cheapest product, the SAP-free underpad.

SAP-containing disposable underpads were therefore chosen for bed-protection, being preferred over the slightly more costly cloth pads because they maintained better skin health. In response to questions Ms Storer Brown felt that a study was needed to check the value of breathable back-sheets on the latest products and that the cloth products had caused skin irritation due to their wetness. She commented that in the trial all products had been changed at the same fixed interval, and that no attempt had been made to utilise the extra absorbency of the SAP-containing products. (Presumably, had this been done, costs would have diminished further but skin integrity may have suffered.)

Evolon® Evolution

Freudenberg's new 1.8m wide Evolon® line at Colmar ( France ) is now starting up. Dieter Groitzsch presented further information on this new technology which hydroentangles splittable spun-laid bicomponents.
• Durable dope-dyed 65% PET/35% PA materials were being developed for use in sportswear and workwear, shoes and window shades, data on their relative comfort having been quantified by the Hohenstein Institute.
• In disposables, both rigid and elastic sticking plaster backings were being developed, the rigid variety to replace the woven-backed products and the elastic to replace the film products.
• For the elastic backing, a “neck-stretching” process was being used to draw down an anisotropic latex-bonded spun-laid fabric into a highly oriented, “parallel-laid” material to provide the same characteristics as a carded product.
• OR drapes and gowns at 35-45 gsm were also under development using splittable PET/PP bicomponents to get the barrier properties required. Both monolayers and laminates with melt-blown (SMS) were being evaluated.

Perhaps of most interest on a line initially heralded as a route to cheap apparel textiles was the development of apertured topsheets for diapers and femcare in the 10-20gsm range. Data on products made from a 16 segment pie fibre comprising 72% PET and 28% PP, laid at 15 gsm and split/apertured in hydroentanglement showed the great strength advantages of this approach over other technologies. Prices? Mr Groitzsch would only comment that they could extrude a nonwoven at the same price as a fibre-maker could make the bico fibre.

SMS topsheet and backsheet

Fibertex ( Denmark ) has been developing new hydrophilic spun/melt laminates to gain better control of pore size and better retention of SAP dust when used as a diaper topsheet. Their 8-13gsm product range features SMMS constructions with 2 gsm of meltblown 4-5 micron fibres supported, in the 8gsm product, by two 3 gsm spunbond layers using 1.8 dtex PP. Higher spunbond weights were used to get the higher basis weights. Pore sizes below 100 micron were possible, compared with above 1000 micron if spunbond alone is used. Hydrophilicity was obtained by adding hydrophilic compounds to the polymer or by kiss-roll application of surfactants. Besides the obvious topsheet applications, Jorgen Madsen foresaw uses in breathable backsheets, packaging and filtration. 

Bicomponent Fibres come of age

John Hagewood of Hills Inc. pointed out that bicomponent fibres were no longer specialities. 250,000 tonnes were now made annually, 100,000 tonnes of this being spun-laid. The now predictable collection of SEM's of splittable, islands-in-a-sea and direct-spun micro-fibres were projected, the most notable being:
• 72 segment pies.
• Pre-stretched PU-tipped trilobal PP fibres which bulk up as the PU tips break loose in later processing.
• 600 PP islands in a PVOH sea: a 1 dpf cardable fibre yielding 100 nanometer fibrils used in a Japanese polishing cloth for high quality optics and CD's.
• An 1120 island 2 dpf version of the above made by NCSU to prove that it could be done.
• 5 micron bico-meltblown (PP sheath, PE core) from a 25-35 hole/inch die. (A future 100 hole/inch die could make 1 micron fibre at economic rates)
• Shaped MB fibres

Bicomponent fibres again

John Wilson of Fiber Innovation Technology also reviewed splittable bicomponent fibre technology, the following points being noteworthy:
• PLA/PET bicomponents split more easily than the PET/CoPET variety in hydroentanglement. (120 bar versus 160 bar requirement)
• Multi-limbed fibres of one polymer can be spun embedded in another and liberated in hydroentanglement.
• The 4DG shape when spun at 3 denier gives 4 micron limbs that may be useful in soft-wiping applications.
• Splittable bicomponents can be split in the refiners of a wet-lay system, but because this would lead to aggregation of the micro-fibres, their use in wet-lay requires late addition and conventional HE splitting.
• 60-80% splitting of some PET/PA6 bicomponents occurs in carding and this can be done commercially providing about 70% of 6 denier PET fibres are blended in to prevent card-loading. This is a zero capital route to incorporating some micro-fibres in webs destined for latex, thermal or needle bonding.
• FIT's segmenting technology allows wrapping of the elastomeric in a 16-segment pie, enabling it to pass through carding before liberation in hydroentanglement.

Microporous breathable films

Kathy Dohrer introduced Eastman's Permtuff™ resins for microporous breathable film manufacture and described experiments to optimise their Moisture Vapour Transmission Rate without sacrificing film strength. Increasing the size of the pores created when the calcium carbonate loaded films are stretched can increase MVTR, but film strength normally deteriorates. Eastman discovered that the characteristic draw ratio of the polymer used, i.e. the draw ratio in the necked region of the stretching film gave a much better correlation with MVTR than the normally quoted overall draw ratio. They therefore developed a resin to maximise the characteristic draw ratio and obtained film with twice the previous best MVTR without loss of tensiles. The resulting Permtuff™ film uses an ethylene/hexene copolymer with an MFR of 2.3 g/10mins and a density of 0.917 g/cc. It gives an ASTM 96D MVTR of 1049 gms/m 2 /day compared with 541 and 437 for the comparable controls. These lab results have recently been reproduced in plant trials, and the new resin should be commercially available next year. In response to questions, Ms Dohrer was unable to help with humidity levels inside a diaper or whether the baby would notice the 500 unit MVTR difference. With regard to the ideal MVTR for diaper backsheet, there was no upper limit short of leaking fluid.

Monolithic breathable laminates

Fermin Ruiz of PGI nonwovens compared the monolithic and microporous approaches to breathable barrier films for diaper backsheets. Their extrusion coating process applied a 0.4 to 0.6mil layer (10-15 gsm) of copolyester on to a lightweight thermal bonded nonwoven. The composite could transmit water vapour at rates between 500 and 2000 gms/m2/day by absorbtion on the wet side and desorption from the dry whereas the established microporous films allowed direct transmission of vapour through the pores at rates up to 4000 g/m 2 /day. However, microporous films, made by loading the polymer with chalk particles and stretching to create voids could leak at the higher porosities. Furthermore they could not be made as thin as the monolithics and for the textile-like diaper backsheets needed to be bonded to the nonwoven with latex. Monolithic films are generally 25% more expensive than the microporous, but because extrusion coating of the nonwoven allows less to be used, they can give more cost effective breathable diaper backings. In the course of the talk Mr Ruiz drew attention to the recent Reuters Health report suggesting that disposable diapers may be reducing the fertility of boys by raising the scrotal temperature, and suggested that breathable backsheets would reduce the problem.

Tributyl tin and scrotal temperature

Pierre Wiertz of EDANA described how the Association had dealt with the Greenpeace-inspired scare related to tri-butyl tin contamination in European diapers. Greenpeace had released the story and called on consumers to return the diapers to the manufacturers on May 12 th 2000. On July 7 th , thanks to prompt joint action by the association and the manufacturers, Greenpeace withdrew the claim, declaring diapers to be TBT-free after all. Nevertheless the militant feminist Womens Environmental Network repeated the story on July 31 st without acknowledging the changed Greenpeace position. The key actions in re-establishing the truth involved EDANA and the diaper makers issuing further joint statements to reassure the consumers, the sharing of test and risk assessment data, the dissemination of information to the European Union and National authorities, and an information exchange throughout the diaper supply chain. The overall conclusion was that maybe a few diapers had been inadvertently contaminated with TBT but at a level that was less than one-fivehundredth of the Tolerable Daily Intake of the chemical. The success of the joint action was illustrated by noting that there were probably fewer than 100 packs of diapers returned. In closing, Mr Wirtz addressed the issue of diapers, scrotal temperature and the reduced fertility of young men, another scare being dealt with in EDANA. EDANA strongly disagree with the conclusions from the Reuters Health study, pointing out that a less than 1 o C temperature difference had been found when comparing babies wearing disposables with those wearing cloth diapers without plastic pants .

Photo-degradable diapers

The Absormex S.A. ( Mexico ) presentation of degradable diapers was most notable for Carlos Richer's demonstration of how the topsheet and backsheet, and indeed the whole diaper could be turned to dust simply by rubbing it between his hands. Biodegradable diapers as developed by P&G and others required a currently non-existent composting infrastructure and so could not be marketed in the USA as biodegradable. They were also more expensive than the standard product, and consumers were notoriously unwilling to pay more. To overcome these problems, Absormex has licenced the TDPA™ technology from Environmental Products Inc. and are developing diapers using this additive in otherwise normal fibre and film. The Totally Degradable Polymer Additive changes the structure of polyolefins so that after exposure to light and/or heat, they fragment easily under mechanical stress. The unspecified additive accelerates oxidative degradation leaving short chains bristling with –OH groups allowing their easy digestion by micro-organisms. Accelerated ageing tests showed the polymer strength falling to zero in 156 hours exposure (ASTM 5208), while the GPC analysis indicated a residual molecular weight of around 5000, down from 150,000. Heat ageing in the absence of light had a similar effect. In the open air, the diapers break-up in about a month, but in a simulated land-fill at 35 o C, about 40 weeks are required – said to be about one-hundredth of the time required by regular polypropylene. However, like “the leaves on the trees” they fail to degrade in the new ASTM biodegradation test, a fact that led Mr Richer to suggest the test needed changing. Films containing the additive have been extracted by PIRA (UK) and have been said to meet the food contact standards, while the additive itself is not classified as a human carcinogen. The diapers, branded “Natural Baby” are currently being test-marketed under close medical supervision and are not available commercially. The downside? Raw materials and diapers will have to be packed in light-proof film and stored in cool conditions from the moment of manufacture until used. Shelf life was said to be controllable from days to months but 4 hours at 60 o C was enough to make the diaper completely unusable. (Some testers had observed this when the products were left in a car on a hot day, and were said to be delighted to find that they obviously worked as advertised!) Asked for samples, Mr Richer provided diapers in ordinary packaging, the contents turning to dust as soon as they were handled.

Polylactic Acid Update

Dan Sawyer stood in for James Lunt to present the Cargill Dow paper on their polylactic acid project. Construction of the Blair Nebraska plant is underway and 200 people are now employed in developing the markets for the new polymer. They have recently organised into 3 business units, Packaging, Fibers, and Emerging Applications. They have also changed the company name from Cargill Dow Polymers LLC to Cargill Dow LLC to reflect the growing importance of non-polymeric chemical intermediates manufactured from lactic acid and lactides. Technically speaking the paper was a re-run of the September 2000 paper given by James Lunt at INTC 2000 in Dallas , and the details were covered in that conference report. In response to questions, Mr Sawyer declared their intention to be “competitive on a price performance basis” with polymer likely to be less than $1/lb. With regard to the earlier projections of 50c/lb, achieving this would depend on the scale of the fermentation process (presumably in addition to using cheaper biomass as explained by James Lunt in response to similar questions on his presentations.) Binder fibres for air-laid had not been developed yet. The laundering and dry-cleaning performance of garments made from PLA was satisfactory. PLA's Biological Oxygen Demand in composting was not known.

PLA and Cellulose compared

Calvin Woodings' presentation comparing polylactic acid with cellulose as a fibre source suggested that the current routed to PLA from cornstarch was not as natural or fossil-fuel efficient as it first appeared. Furthermore while the PLA fibre, but for a lowish melting point and borderline hydrolytic stability, was an excellent fibre and a remarkable technological achievement, it would have to be available at little or no premium over PP and PET to be the major long-term success hoped for by manufacturers Cargill Dow. Their statements on resin price from the Blair ( Nebraska ) plant suggested that the fibres would be comparable with rayon, lyocell or bleached cotton in price. Their unique selling point over regular PET would be their origins in cornstarch and an ability to degrade under industrial composting conditions. Over cellulosic fibres, their thermoplasticity would be the key. Future plants using waste biomass as the starch source could improve this positioning, but by then, aliphatic polyesters may be extractable directly from plants, avoiding the complexities of pure lactide and polylactide production.

RF Drying applied to nonwovens

Radio Frequency (RF) drying works by directly heating the water in a wet material: Ben Wilson of PSC Inc. described its possible applications in nonwovens production, both alone and in combination with traditional drying systems.
• Problems of latex migrating to the surface of thicker chemically bonded nonwovens can be overcome by using an RF drier to preheat and dry the latex prior to conventional curing on cans or ovens.
• Very thick, insulating materials (such as a cellulose sponge) can be dried much more rapidly than by conductive or convective heating.
• Heavyweight wet-laid nonwoven production can benefit from an RF boost in between can-stacks to move the internal moisture to the surface for easier conductive removal.
• An RF finisher-dryer can reduce nonwoven moisture variability by preferentially drying out any wet spots.
• RF heating in a cool airstream allows low-melt or heat sensitive materials to be dried at low temperatures. (also reduced discoloration and odour generation in cellulosics?)

Recovering and recycling waste

John Cork of Ibis International and Jim Westphal of Troika Nonwovens Inc. reviewed their system for recycling air-laid nonwoven production waste to reclaim fluff, fibre and SAP. John Starr's figures for global air-laid production; 325,000 tonnes in 1999 rising to 410,000 tonnes in 2001 were quoted, along with his capacity split estimate: 57% of air-laids using both latex and thermal bonding, 19% using latex only, 0.5% using thermal only, 9.5% each going to Coform (with melt-blown PP, a Kimberly Clark process) and hydrogen-bonded (i.e. binder-free). A 20,000 tpa air-laid machine would make at least 2000 tpa of scrap, which when valued at 70% of the cost of the fluff-pulp would be worth, they say, $525/tonne, or ~$1m/year. A recovery unit suitable for this would only cost $1m. It would make bales of fluff for sale or debaling and refeeding.

Recycling waste diapers

On the basis that Europe had 150 diaper production lines each making 2-4% diaper waste, Martin Bosch of Ventilatorenfabrik Oelde GmbH estimated 15-30000 tonnes of diaper materials were available for recovery. These would comprise 1-3% of plastics, 50-70% pulp fibres and 25-50% SAP, the latter two items being worth 0.5 and 2.5 Euros/kg respectively. Recovery of this waste from a single diaper line would yield savings of 165,000 Euros/year, and Mr Bosch could sell you a plant to allow you to do this. With a throughput of 250 kgs/hour, this plant would recover 85% of the SAP and 95% of the pulp at quality levels suitable for recycling. ROI, calculated on the basis of 150 kg/hr throughput on a 2 shift system would be 18 months. The system had been developed with the aid of a European Community grant and with the support of Paul Hartmann AG who appeared to have the prototype in operation. Mr Bosch was now working on a system for air-laid core recovery.

The following papers were in a simultaneous session and have been summarised from the printed text.

Replacing viscose with pulp

Jurgen Heller of Fleissner estimated the annual savings that could arise from using 50/50 PET/Pulp to replace 70/30 PET/viscose in a hydroentangled wipe fabric. Despite the higher energy requirements of air-laying pulp, combined energy and raw material costs for a 9000 tpa unit running the pulp blend were $6m lower, or two-thirds of the costs of running the viscose blend at the same speed. (In reality, the pulp blend should run 50% faster than the viscose blend so the claimed savings were felt to be conservative). However the pulp product would require a costly air-lay unit, two hydroentanglement units instead of one (one before and one after the air-layer) and a costlier water filtration system. A comparison of these costs was not provided.

Homofils like bicomponents

The evolution of two new members of FiberVisions family of polypropylene fibres was covered by Erik Grann Gammelgaard. HY-Soft is a lower modulus homopolymer fibre with a softer polymer skin, capable of giving better softness/strength ratios than bicomponents. HY-Strength has a slightly degraded skin allowing it to form stronger bonds in thermal bonding and hence give nonwovens with significantly higher CD strength. Peak carding speeds of 335 m/min and an ability to form lighter weight topsheets allow the production of lower cost fabrics. These encroachments into bico territory has not gone unnoticed. FiberVisions JV with Chisso is now developing better ES bicomponents also. ES-Tendon-C, ES-Delta, and ES-C Cure were said to be “on their way”, but not described further.

Dry-laid/air-laid laminates

Dr Alvin Hu of KNH Enterprise Co Ltd ( Taiwan ) has measured the losses of SAP and pulp particles from a thermal bonded Cardweb/Air-laid/Cardweb composite intended for use in sanitary napkins and panty-liners. Heavier webs and those made of finer fibres retained more SAP, leading to the conclusion that these CAC composites meet the requirements for commercial products.

Cotton/spunmelt laminates

Ed McLean Jr of Cotton Incorporated described their joint work with TANDEC on cotton/PP spunmelt composites for hygiene use. The conclusions from testing these cotton-surfaced and cotton-cored laminates: “The weight of cotton had a notable effect on the wicking, absorbent capacity and retention capacity of the product”. It was postulated that the “…hydrophilic nature of cotton may be responsible…”. Furthermore, the use of spunbond PP “…resulted in higher strength…” than achieved with meltblown PP.

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