Nonwovens from recycled fibres and PLA

Bernd Gulich of the Sächsisches Textilforschungsinstitut e.V. (STFI – Germany) has been collaborating with Oerlikon Neumag to develop air laid nonwovens made from recycled short fibre material.  After air-laying with 20% bico and thermal bonding:-

•         Waste paper gives a cardboard like material.
•          Wool dust from felting is around 5mm long can be used for insulation and oil absorbents
•          Shredded tyre cord from tyre recycling has been converted into oil absorbents.
•          Shredded textile glass fibre makes insulation nonwovens.
•          Dried grass (not hay) makes mouldable boards for automotive use.
•          Nettle, poplar, coconut, kapok, hemp and of course cotton linters all make usable nonwovens or boards.
•          Basalt fibres make insulation boards.
•          Metal fibre sheets are under development.
•          Leather waste with only 5-10% bico is air laid, hydroentangled and thermally embossed to look and feel like real leather.  This process is now running on a commercial scale in the UK.

Roshan Paul of Leitat Technological Center, Terrassa (Spain) was blending 5% cellulose powders into PLA during extrusion but provided no data on the performance of the resulting biodegradable plastic.  He had also prepared masterbatches of thermochromic dyes with PLA to make fibres for fire-protection clothing but admitted that the clothing gave no indication of skin temperature.  (Funding was provided by the EU 7^th Framework.)

Light- and FIR- emitting fibres

Delphine Chevalier of Brochier Technologies, Villeurbanne (France) described light-emitting textiles made by Jaquard weaving 0.25 to 1mm optical fibre monofils with normal textile fibre yarns to create an infinite variety of patterns or words.  The cladding is removed from one side of the optical yarn in finishing so that light can escape wherever illumination is required.  The ends of the optical yarns are then bundled and connected to LED’s.  All-optical fabrics can give even illumination over large flat or curved areas from a textile less than a millimetre thick and weighing less than 500 gsm.  Environment and health applications e.g. air and water purification follow from the use of UV LEDs, and IR LEDs lead to safety and sensor applications.  Blue-light emitting bedsheets can be used for phototherapy, especially for babies with jaundice, the treatment of skin diseases and for winter depression.

Gabriel Gorescu of Rhodia Fibras, St. André (Brazil) said  Rhodia, a member of Solvay Group, has the technology for producing melt spun polyamide microfiber embedded with special bioceramic materials.  These “Emana” PA66 fabrics with excellent texture show a high level of FIR emissivity when warmed by the body and thus give significant skin health improvements in clinical (cosmetic) trials.

On the sport field, besides the improvement of body thermoregulation already known as a FIR yarn benefit, this yarn has shown significant benefits during aerobic running exercise and during repetitive eccentric muscle movements.  In other words, Mr Gorescu was claiming “Emana” fabrics enabled athletes to run faster when they are tired and body-builders to work harder without damaging muscles. “Emana” also heals wounds.

Nanotubes, flushable wipes and PLA/PHBV blends

Analysis of Nanoparticles in Meltspun Filaments

Johannes Wulfhorst of the Institut für Textiltechnik (ITA) der RWTH Aachen, Aachen (Germany) reported on the ways of checking the orientation of carbon nanotubes in polymers used to make electroconductive fibres.  An FEI Tecnai F20 electron microscope is used to create a series of 2D views as the sample is tilted through 120 degrees.  Tomographic imaging software compiles these into a 3D model to allow exact nanotube orientation analysis to be carried out.  The work shows that nanotubes do indeed get oriented in the axial direction during fibre extrusion.  ITA has also observed that carbon nanotube inclusion alters the bimodal melting character of polyester.

Improved Dispersibility of Wet Wipes

Roland Scholz of Kelheim Fibres GmbH, Kelheim (Germany) reviewed fibre types and their effect on the dispersibility of wet wipes made by carding and hydroentanglement.  0.9 and 1.7 dtex round fibres were compared with 1.7 dtex “gel-surface” fibre, solid flat fibres with a 5:1 aspect ratio, inflated-collapsed fibres with a 20:1 aspect ratio and a new fibre of undisclosed dimensions in lengths of  12, 16 and 20mm.  The shorter the fibre the easier was the dispersion in the tube test, similar results being obtained from the Netherlands sewer pump test.  The round fibres and the “new shape” fibres dispersed best at these lengths.  Standard 40mm fibres formed ropes.

Fully Bio-Based and Degradable PHBV / PLA Fibers

Peng Chen of the Ningbo Institute of Materials Technology and Engineering, Ningbo (China) has discovered that polyhydroxy butyrate valerate fibres (PHBV) are too brittle and rigid to make good nonwovens.  Surprisingly blends of PHBV with PLA – which is also brittle and rigid – are soft and give nonwovens with reduced shrinkage.  The mixture of polymers is extruded with additives to promote “reactive blending”, at speeds up to 3000m/min.  The resulting yarn can be stretched up to 3 times off-line to make the final soft but glossy yarn.  The unexpected softness is thought to arise from the oriented fine lamellae structure induced by extensional flow during spinning and drawing.  It feels like rayon or silk but is naturally hydrophobic.

Denkendorf at Dornbirn

Harvesting and Storing of Solar Energy

Thomas Stegmaier of the Institut für Textil- und Verfahrenstechnik (ITV), Denkendorf (Germany) described a 3-layer textile roofing fabric engineered to allow air to be pumped through the middle layer.  This air reached 150-160^oC on a hot day and was used to dry out a silica-gel “energy store”.  This stores the energy “without loss” and yields warm dry air months later when humid air is pumped through it.

Asked about the efficiency of heat recovery, Mr Stegamaier said this had yet to be calculated.

Micro Fibers Based on Cellulose and its Acetate

Frank Hermanutz of the Institut für Textilchemie und Chemiefasern (ITCF) Denkendorf, Denkendorf (Germany) has used spinnerets made by new laser hole drilling technology for the direct spinning of cellulose and cellulose acetate fibres.  The holes are drilled with an ultra-short pulsed laser using a highly focussed beam circulating helically around the circumference of the required hole.  The system was developed at IFSW in Stuttgart. The resulting holes have a naturally conical inlet and a precise outlet down to 25 microns in diameter.  Half-inch thimbles with 2000x25 micron holes in gold/platinum looked excellent for wet spinning and for air-gap, a 250 hole stainless steel version had been made.  Cellulose microfibers down to 0.2 dtex have been wet-spun from a solution of cotton linters in an ionic liquid (8% to 16% in 1-ethyl-3-methylimidazolium acetate) and from cellulose acetate in acetone.  The latter had a very rough non-circular cross section.

Finer, Stronger Melt Blown

Christoph Rieger of the Institut für Textil- und Verfahrenstechnik (ITV), Denkendorf (Germany) promoted ITV’s recently developed ability to produce melt blown PP down to 0.4 microns and stabilised melt blown PET webs of high strength and thermal stability to 200^oC.  They are also capable of hydroentangling melt blowns and their laminates with other fabrics to get the best combinations of strength and fineness.

Bicomponent Fibers by overjacketing extrusion and electrospinning

Felix A. Reifler of EMPA Laboratory for Advanced Fibers, St. Gallen (Switzerland) was using overjacketing extrusion to add a sheath or sheaths to a monofil core. The technology was essentially that used to apply insulation to fine copper wires.  The main application appears to be applying an insulating sheath to silver-coated yarns for use in conductive textiles.  An 80 micron polyester is plasma-sputter coated with silver and overcoated with 8 microns of thermoplastic PA12-based elastomer at 25 m/min.  Dip-coating can also be used.  PLA and PVA sheaths have also been tried.  Adhesion of the sheath needs improving and the work continues.

Juan Esteban Diaz Gómez of NanoMyP Nanomateriales y Polímeros S.L., Armilla (Spain) has been spinning bicomponent nanofibres from annular nozzles where the core polymer solution can be a non-electrospinnable polymer.  Hollow nanofibres, and liquid filled nanofibres (hydrophobic liquid inside a hydrophilic polymer) are also possible.  They are now working on scaling up the process and further improving it with air-jets (“electroblowing”) or rotation (“Forcespinning™).  “Smart materials with physicochemical properties tailored to customer needs” is now the subject of a new department.  P&G, Unilever and Henkel were among the companies listed as customers of NanoMyP.

Liquid Crystal Nonwoven from Kuraray

Yasuhiro Shirotani of Kuraray Co., Ltd., Saijo (Japan) said Vecrus™ was a melt-blown nonwoven made from the Vectran™ liquid crystal polymer.  The nonwoven withstood temperatures of 330C and shrunk less than 1% at 260C. Vectran™ is a wholly aromatic polyester made from 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid.  It is used for printed circuit boards, electromagnetic shielding and electric motor insulation.  It’s moisture regain is only 0.002%.  A new version of the melt blown is now being developed with half the standard fibre diameter (3 microns: down from 7) The melt-blown webs will be made in the 3.5 to 20 gsm range and will have a breaking length of over 10 km, double that of the standard Vecrus™

Applications will include fibre reinforced plastics for phones and laptops, Li-ion battery separators, heat resistant wipes in copy machines and heat resistant filters.  In the copy machines the new wiping roll uses a 6gsm 20 micron thick Vecrus™ which gives 3 times the usual length of wiper in the cartridge.

Kelheim Viscose for Dry and Wet Nonwovens

Philip Wimmer of Kelheim Fibres GmbH, Kelheim (Germany) reviewed the changes in absorbency through Kelheim’s range of Italian fibres to illustrate that pure cellulose fibre can give from 1:1 to 4:1 water retention compared with cotton’s 0.5:1.  He then moved on to consider the possibilities of less absorbent, more hydrophobic types.  More crystalline fibres are less accessible to water and stronger, but this approach can do no more than halve the retention.  Adding non-absorbent fillers can do the same, but these more than halve the strength.  Chemical modification works, e.g. acetylation but the result is not pure cellulose.  Hydrophobic agents can be applied as finishes or added to the viscose, the latter approach giving a more permanent change in hydrophobicity which can resist washing and dry cleaning.  Kelheim have now developed such a product using an additive made from renewable, biodegradable raw materials which is also FDA approved for hygiene and food contact applications.


Ingo Bernt of Kelheim Fibres GmbH, Kelheim (Germany) ran through the properties of the Italian fibres again, the new additions this time being a 4dtex Leonardo smooth flat fibre and “Umberto”, a variable cross-section fibre giving an alphabet soup of shapes.  Umberto was not included in the written paper.  The finer Leonardo gives papers of higher strength and folding endurance than the 9dtex, but slightly lower transparency.  Anionic treatment as used to make the Verdi fibre boosts strength and folding endurance further.

Cellulose Acetate Nanofibres from Agricultural Waste

Roberto Frassine of the Politecnico di Milano Polymer Engineering  Lab., Milano (Italy) has been using corn-cobs and straw, wheat straw and even seaweed as a source of cellulose for acetylation – a process which normally requires the highest quality dissolving pulp.  The cellulose extraction and purification process involves Toluene/Ethanol extraction of waxes followed by bleaching first with alkaline peroxide and then with an acetic/formic acid/hydrogen peroxide mixture. 

A final peroxide extract yields a pure cellulose with a DP rather lower than that obtained from wood.  This was acetylated  and dissolved in dichloromethane/methanol for electrospinning to nonwovens.  At acetate concentrations of 7% and 10% the nonwovens were of good quality.  A lab. scale batch reactor has now been built to allow 1.5kg batches of acetate to made for future experimentation.

Tencel for Battery Applications

Marco Gallo of Lenzing AG, Lenzing (Austria) described the development of separators for alkaline batteries using Tencel.  Tencel can be refined in disc refiners and beaters to give a hgher proportion of microfibers and fewer cut fibres than pulps.  This leads to lighter, thinner papers with smaller pores and hence better insulation and conductivity than alternatives.  Cellulosics are normally blended with PVA fibres and bonded with PVA latex.  Tencel can be used in blend with pulp or viscose in the cellulosic portion according to the cost/benefits required.
New varieties of Tencel are under development which will allow further reductions in the weight of the separator required per battery.  These also improve the dimensional stability and durability of the paper in the strong alkalis used.  There were numerous questions:

•         Can Tencel be used to obtain nanofibres?  Yes but at a cost which only works for some applications.
•          What operating temperatures must the separator be designed for? -30 to +50C
•          Is the whole furnish refined together?  No Tencel is refined separately.
•          Is Tencel paper used in double-layer electrolytic capacitors?  Yes.
•          Are fibrils lost through the wire?  Yes this is an issue which necessitates careful tuning of the refiner.
•          Would Tencel be used in electric car batteries?  Yes – this is under development.

          See also Innovation:  Product development with Tencel 1988

Carbon Footprint of Garments

Jürgen Ströhle of Benninger AG, Uzwil (Switzerland) said the carbon footprint of garments depends crucially on the country of manufacture.  

• Brazil is best by far because most energy generation is from biomass.  India and China are worst because they use most coal.  
• For fibres, PET appeared worst followed Asian viscose and US and Chinese cotton.  
• Austrian viscose had the lowest carbon and water footprint, while US cotton had the highest water footprint.  
• Studies of T-shirt finishing methods revealed that 100% viscose shirts had least impact, 100% cotton most, with 100% PET in between.  
• For dress shirts, cotton was worst with Tencel and PET equally good.  

Asked if organic cotton would be better, Mr Ströhle thought it would make no difference to the finishing impact but would be better at the raw material stage.  On a cradle-grave basis, half the impact of a T shirt is at the production stage and half in washing/drying.

Tencel Gel

Martina Opietnik of Lenzing AG, Lenzing (Austria) reviewed the development of Micro Fibre Cellulose from Turbak’s development of a nanocellulose gel in 1983, through their use in biocomposites in the 90’s and in transparent cellulose nanofibre paper in the 00’s, to their current applications in flexible organic light emitting diode displays.  Traditionally pulp is acid-degraded, beaten and homogenised to make MFC but now the lyocell process can be used to make either fibres or beads which require much less energy to convert into MFC. 

Tencel fibre gives a fibrous gel but the Tencel beads give a 3-D structure and a perfectly smooth gel.  They are both white viscous suspensions which are stable over a range of pH’s and temperature, but show thixotropic behaviour.  They also form films on drying, and can be used as coatings for films, textiles, papers and tablets.  Applications in packaging, cosmetics, food thickening, and medicines are envisaged.  In food it could also be a calorie-free fat substitute.

Asked if the coatings would be stable on polyesters, Ms Opietnik thought the gel would stick well to the surfaces of films or fibres but would have to cross-linked for durability.  Application could be by spraying.  Is the gel regarded as a fibre under the REACH regulations?  Maybe a new directive was needed to clarify this aspect.

Cellulose Nanofibre Nonwoven Fabrics

Satoru Yoshida of Asahi Kasei Fibers Corp., Moriyama City (Japan) has produced nanofibres by refining woodpulp into the 30 to 100 nm fibril range and producing wet-laid sheets down to 3 gsm with comparable surface area and porosity to electrospun nanofibres.  The sheets also show unusually high heat stability (better than hydrophilic PTFE film) and a usefully lower coefficient of thermal expansion than cellophane film.

The manufacturing process for CNF involves conventional beating of wood pulp to a highly fibrillated state, followed by high pressure homogenisation of the resulting slurry. From the micrographs, this completely destroys any residual fibre backbones to yield an all-fibril dispersion – “Micro-Fibrillated Cellulose”.

Applications developed so far include a transparent hybrid epoxy/CNF film with high transparency and low thermal expansion (50-200C), and functional filters where the surface of the CNF is chemically modified, e.g. crosslinked to improve wet strength.  Battery separators and capacitor dielectrics were mentioned as end-products.

Biosoft (TM): Hydrophobic Tencel for Nonwovens

Bianca Schachtner, Lenzing AG, Lenzing (Austria) introduced a water-repellent version of Tencel branded Biosoft and said to be extraordinarily soft, hydrophobic, biodegradable and botanic.

•        As an oil absorbent, Biosoft(TM) floats on water and takes up 3-4 times as much oil as Tencel.
•          It withstands hydroentanglement.
•          In a pack of wet wipes, a 70/30 Tencel/Biosoft blend wipe shows reduced variability of lotion uptake through the pack compared with 70/30 Tencel/PES.
•          Tencel has a surface tension of 90 mN/cm compared with 30 for Biosoft.  However blends of the two do not give a linear change of ST.  70/30 Tencel/Biosoft has almost the same water uptake as 100% Tencel.
•          As a biodegradable topsheet, Biosoft gives similar strikethrough and wetback results to synthetic topsheets.
•          Biosoft topsheet offers improved embossability compared with Tencel.

There were numerous questions.  The treatment affected the surface only.  2^nd and 3^rd insult strikethrough and wetback were the same as the first.  It absorbs water vapour like Tencel.  It feels very soft when in textiles or nonwovens. The cost relative to PP was not divulged.

Kelheim Fibres: A Specialist Specialises

Matthew North of Kelheim Fibres GmbH, Kelheim (Germany) reviewed the last 30 years from the viscose fibre viewpoint observing that after a global decline of 30% between 1980 and 1999, a sustained recovery was underway with capacity doubling to 3.8 million tonnes since then. By 2020 a further 1.4 million tonnes capacity will be added in China and SE Asia. This new capacity will focus on a few very large lines to make standard products for textiles and commodity nonwovens. The theme is pile it high and sell it cheap.

Kelheim Fibres is in comparison a small specialist producer with 11 flexible lines which allow it to produce small lots of fibre with unique properties. It has become the world’s leading producer of tampon fibres, flock fibres, short-cut papermaking fibres and viscose-based carbon fibre precursor. For the future it will focus on new applications for papermaking, filtration, composites and speciality textiles. With R&D being central to these developments it intends to establish a new R&D centre for bio-based polymers and fibres in Kelheim.

Absorbent Fibers Based on Cellulose Acetate

Jens Schaller of Thüringisches Institut für Textil und Kunststoff Forschung e.V. (TITK), Rudolstadt (Germany) has been dissolving cellulose acetyated to varying degrees in ionic liquids prior to spinning. Over a range of degrees of substitution from 0.07 to the commercially standard 2.5, absorbency peaks between 0.5 and 0.7DS and then falls to the normal acetate value at 2.34. At peak the WI is 300-400%, and hence much higher than obtainable with pure cellulose fibres or their alloys with water soluble polymers. Furthermore the absorbency level is unaffected by ionic concentration, and the fibre properties are like viscose. The fibres have a rough surface and mercury porosimetry shows a porous structure similar to lyocell. 2.5DS “standard” acetate can also be spun, wet rather than dry, from the ionic liquid (1-butyl-3-methyl-imidazolium chloride or BMIMCl). This process avoids the explosion risks of standard acetate production.

Recycling the BMIMCl involves vacuum distillation of the 10% spinning solution up to 80%, and then using a thin-film evaporator to get to 97%.

Asked why the WI increases with DS up to 0.7, Mr Schaller said a few acetate groups destroy the hydrogen bonding and increased accessibility to water but over 0.7 DS, increasing hydrophobicity takes over. Could lithium chloride be used as the solvent for spinning? Yes but it’s more expensive and harder to recycle (thin film evaporation not possible) Why bother with acetate when SAPs are available more cheaply? This approach gives fibres more easily and they are not salt-sensitive.

Filters using Self-assembling Supramolecular Nanofiber Webs

Hans-Werner Schmidt of the University of Bayreuth, Macromolecular Chemistry, Bayreuth, (Germany) described the creation of nanofibres from complex monomers designed to self-assemble by hydrogen bonding in one dimension only, the resulting polymers clustering together into bundles. Initially the bundle diameters would be 10-20nm but these too would aggregate into larger bundles up to a micron in diameter.

The 1-3-5 trisamide derivative of benzene could be dissolved in 2-butanone at 0.4% and would self-assemble into nanofibres on cooling from 240C. This could be applied to the surface of a nonwoven to form a filter (2.8% nanofibres concentrated at the surface.) An example with 1% derivative in 2-butanone giving 7.6% nanofibre on nonwoven was shown to give an impressive network on the surface, the pore size of which depended on the solution temperature over a 25-120C range. Here the nanofibres formed in the pores of the nonwoven surface.

Asked about the temperature sensitivity of the nanofibres, Mr Schmidt said he had shown lower melting point products, but others were stable up to 350C. He was working on a water-based solution to replace the 2-butanone.

Asahi ”Bemliese” Cellulosic Spunbond

Kyoko Machioka of Asahi Kasei Fibers Corp., Nobeka, Miyazaki (Japan) described the new microfibre version of the cuprammonium cellulose spunbond nonwoven.  

Cotton linters are dissolved in cuprammonium hydroxide to give a 10% solution with twice the DP of viscose, and this very high viscosity solution can be extruded through large holes (0.5-0.7mm) and drawn as a liquid by over 100 times before regeneration to cellulose.  

The new microfiber nonwoven has filaments of 3-5 micron diameter and gives fabrics with a third of the pore size of regular Bemliese®.  Fibres are spun at 150 m/min after drawing by 500 times onto a belt running at 20-40 m/min.  The fabric absorbency was said to be outstanding but no test data was provided.  Vertical wicking appeared to be 50% higher than for the regular Bemliese.

How much copper remains in the nonwoven?  Zero.

Toray "Foresse": Melt Spinning of Thermoplasticized Cellulose

Yoshitaka Aranishi of Toray Industries Inc., Mishima (Japan) described Toray’s range of polymers made from biomass, including the world’s first 100% bio-based polyester, but focussed on the development of melt-spinnable cellulose esters.  Nonwovens have in the past been made from melt-spun cellulose acetate, hydroxypropyl-cellulose, phenylacetoxy-cellulose and trimethylsilyl cellulose but these fail to give the necessary high-speed and stable production.  Toray has now optimised a mixture of cellulose esters which when blended with a plasticiser can be spun at high speed (2000 m/min mentioned) into a wide range of fibres with a wide range of cross-sections or bicomponency, and then de-plasticised.  Hollow fibres, X-shapes and Islands-in-a-Sea bicomponents with PLA were shown.  Full orientation occurs within 20 cms of the spinnerette compared with over a metre for PET.  The only fibre properties provided during the talk were moisture regain being 10 times that of PET (i.e. very hydrophilic), the refractive index being lower (more lustrous and vivid after dyeing) and a modulus less than half that of PET (giving much softer fabrics).  More information on this “Foresse” fibre emerged in questions:

·         

Long-term Fibres Demand: The Cellulose Gap

Peter Driscoll of PCI Fibres, Mayfield (UK) continued the “Cellulose Gap” arguments started at last year’s Dornbirn conference by confirming his view that despite the spike in cotton price, there has never been a shortage of the fibre and won’t be one in the foreseeable future.  In late 2010 there appeared to be a shortage which caused the spike, and this caused a fall in demand which cost the cotton industry about 10 million tonnes of sales because the predicted 30 million tonne demand fell to an actual 20 million in 2011.  Global cotton pipeline stocks rose from 4 to 14 million tonnes between 2004 and 2011.  It’s share of total fibres is now 30% and is expected to remain at that level through 2020.  Stocks will decline to about 8 million tonnes by 2020.  So, cotton stocks alone are likely to remain well above the annual production of man-made cellulosics for the foreseeable future and will be used before man-made cellulosics to fill any gaps which might arise.

Total fibre production including cotton moved above 78 million tonnes in 2011 and could reach 100 million in 10 years time.  Polyester filament is the key growth area, the  majority

Slow Fashion and Sustainism: Sustainable Procurement of Textiles

Susanne Müller of the Hochschule Niederrhein, Mönchengladbach (Germany) talked about the importance of the “slow fashion” movement to sustainable procurement. This means wearing clothes for longer, having bought timeless, high quality designs such as the LBD (little black dress). Environmentally sensitive fibres such as bamboo, hemp, organic cotton or “Qmilch” (milk-protein fibre) should be converted in socially-sensitive factories with minimal use of water and energy, cradle-grave processes (?) and safe, clean working conditions. All texiles should be lighter to reduce transportation impacts, and the use of cotton, rubber and leather should be minimised because of their high environmental impacts; use synthetics instead.

“Sustainable consumers” are going on a fashion diet (one dress lasts all year), buying second-hand clothes or swapping with friends.  The “swap not shop” movement appears to be gaining momentum with swapping parties and exhibitions proving a fun thing to do.  Modernism equated with “you are what you own”.  Sustainism is “you are what you share”.

Sustainism currently targets LOHAS people (those enjoying a Lifestyle Of Health And Sustainability), with LOVOS coming up fast (Lifestyle Of VOluntary Simplicity).

However sustainism on its own is not appealing: it has to linked to a fashion trend.  Patagonia provide an example of the way forward “We make excellent clothes – you buy less of them”.  Their marketing encourages repair and recycle.

(From Dorbirn Conference Sept 2012)