Polyamide Fibre Developments
Polyamide filaments and fibres are used in a wide variety of end-uses but the global production level is relatively small in comparison with that of polyester fibres. In 2010 polyamide accounted for 9.3%, polyester 86.1% and acrylic fibres only 4.6% of the global production of manufactured fibres.
According to Tecnon OrbiChem, both polyamide filament yarns and staple fibres have lost share in the global fibres market.1 In 1980 polyamide accounted for more than 10% of global fibre production, but by 2000 this had fallen to 7.4%, with a further decline to 5.1% by 2009. Production in 2009, however was around 3.7 million tons, up from around 3 million tons in 1980. Tecnon OrbiChem has forecast that by 2020 the total global production of polyamide filament yarns and staple fibres will reach more than 4.4 million tons.
Polyamide filament yarns are used in a wide range of applications, especially in carpets and industrial end uses in which the strength and durability of polyamides are important factors, eg. high-performance tyres and airbags, where demand is increasing. In the USA production of polyamide filament yarns has fallen but, because more than 80% of polyamide filament consumption is in the carpet sector, this is unlikely to be substituted by imported yarns in the future. This is because of the highly capital-intensive nature of the polyamide manufacturing process and the high transport costs associated with the bulky product.
Production of polyamide filament yarn in Western Europe has fallen by around 2.5% per year during the period 2005-2010, less than in North America (5.2% per year but likely to fall to around 3.5% per year over the next decade). Although China is the largest producer of polyamide filament yarns it is also still the number-one importer, accounting for 24% of the global imports total in 2008.
Both polyamide 6 and 6.6 are produced globally, but the dominant polymer in Asia is polyamide 6, which has a simpler manufacturing route and is cheaper to produce. For these reasons, the majority of the growth in polyamide has been in polyamide 6 fibres. The output of polyamide 6 fibre in Asia is anticipated to grow at around 8% per year, whereas the output of polyamide 6.6 is likely to stabilise. China’s burgeoning automotive industry, with increasing demand for cars and commercial vehicles, could prove to be a major growth area for polyamides.
Textile filament yarns account for around 1.5 million tons of polyamide, while polyamide industrial filament yarns and carpet filament yarns are each around one million tons or less.2 By contrast, the use of polyamide staple fibres appears to be steadily declining, one of the main uses probably being in 80/20 wool/nylon blends for wool-rich carpets and knitwear.
New Dyestuffs for Polyamides
Brilliance of colour is important for many fashion end uses such as sportswear and swimwear. Clariant has recently introduced a new acid, metal-free dyestuff with an outstanding brilliant-yellow colour when applied to polyamides, wool and their blends. This novel dyestuff, Lanasyn Flavine F-5G, is perfectly compatible with Lanasyn Turquoise M-5G and offers textile designers, dyehouses and textile printers the opportunity to produce exciting bright greens. Lanasyn Flavine F-5G thus opens up new design and fashion possibilities that could not be attained before in the bright-yellow and green areas on polyamides and wool.
The combination of Lanasyn Flavine F-5G with Lanasyn Turquoise M-5G exhibits tone-on-tone rate of strike, together with no mutual blocking, coupled with high build-up. Both these dyestuffs respond to pH changes in a similar way, which makes the dyestuff combination ideally suitable for pH-shift dyeing, using Clariant’s Opticid VAN liq c. An important aspect of performance on 80/20 polyamide/ elastane swimwear is high colour fastness to light as a self-shade, coupled with tone-in-tone fading of Lanasyn Flavine F-5G when used in combination with Lanasyn Turquoise M-5G.
Lanasyn Flavine F-5G exhibits the highest brilliance of all non-fluorescent acid-yellow dyestuffs currently available and makes it possible to match on polyamide and wool fibres the brilliant yellow and greens dyed with reactive dyes on cellulosic fibre. Lanasyn Flavine F-5G imparts high wet-fastness performance on polyamide and wool fibres and is recommended for polyamide, polyamide/elastane and wool. This novel yellow acid dyestuff is also suitable for CMYK printing systems.
Clariant is launching another new dyestuff for polyamide dyeing, namely Nylosan Brilliant Red S-3R. This unique dyestuff is claimed to outperform existing milling red elements with far superior build-up properties for the deepest red shades. Nylosan Brilliant Red S-3R offers excellent compatibility with Clariant’s other Nylosan S dyestuffs with, in addition, greatly enhanced colour fastness and build-up compared with CI Acid Red 131 and CI Acid Red 249. Colour-fastness tests carried out on 80/20 polyamide 6/elastane dyed with Nylosan Brilliant Red S-3R confirm its superior performance over CI Acid Reds 131 and 249 in the AATCC Cold Water test, ISO 105 E04 alkaline perspiration test and ISO CO6 B2S washing fastness test.
The low transition temperature of polyamide fibres creates problems in home laundering and other thermal treatments because of thermomigration of conventional dyes from the fibre interior to the fibre surface. This generates poor colour fastness to wet treatments. Huntsman Textile Effects has launched a range of patented reactive-acid dyestuffs, which have been engineered to provide high levelness and shade reproducibility, combined with superior wash and wet fastness under all the usual laundering conditions.
Huntsman Textile Effects can now ensure intense deep shades even on full-dull, microdtex polyamide using its innovative, patented ‘ERIOFAST micro’, exhaust-dyeing process. This ensures maximum wash fastness, even at the highest washing temperatures encountered in domestic/industrial laundering treatments. Unlike conventional dyes that require fixing aftertreatments to achieve higher wash f astness, the ERIOFAST micro-dyeing process avoids the stiffening and adverse effects on absorbency that can accompany such fixation treatments.The ERIOFAST micro-dyeing process thus preserves the fibre softness and hydrophilicity.
The ERIOFAST range covers the full shade gamut, with seven bright dyestuffs (two yellows, one orange, two reds, two blues) and a black dyestuff. The dyestuffs exhibit migration during dyeing to provide exceptionally high levelness even in critical dyeing processes, such as in beam dyeing. The ERIOFAST range enables a wide shade gamut to be matched, combined with high flexibility in matching the metamerism of target shades. The high wet fastness of such dyestuffs has opened up opportunities for design-colour blocking in growing highvalue segments such as intimate apparel, swimwear, sportswear and leisurewear. This state-of-the-art in wash fastness can help to increase customer satisfaction and reduce retail claims considerably.
Auxiliaries and Finishes
Huntsman Textile Effects has developed a patented pH-slider, Albatex PS-35, which releases acid only at temperatures above 50°C, with a very slow speed, the final pH being reached only during boiling. Albatex PS-35 avoids the storage problems associated with some products that can release acid during storage, which can negate the pH-sliding effect during subsequent dyeing. The high strength of Albatex PS-35 ensures any pH can be reached economically, enabling it to be suitable for very-pale to very-dark shades, in any application. The pH value during dyeing can be decreased from seven to any desired acidic pH for any dye class/shade depth. Uniform build-up and levelling ensures excellent, reproducible surface levelness while full, controlled exhaustion assures batch-to-batch shade reproducibility.
Univadine MC is a levelling agent from Huntsman Textile Effects for exhaust dyeing of polyamide yarns and fabrics. The product is amphoteric in nature and has affinity for both dyes and fibres under acid conditions, which promotes a balanced migrating effect, on-tone build-up and excellent levelling properties, covering physical barriness to give superior surface levelness. Exhaustion is retarded during the heating-up phase of dyeing but very good final exhaustion values ensure high shade reproducibility.
For the improvement of wet fastness of polyamide dyeings and prints using acid and metal dyes, Erional FRN (Huntsman Textile Effects) is highly stable under acid conditions and particularly recommended for polyamide/elastane blends. Suitable for all kinds of polyamide fibres, including polyamide microfibres, Erional FRN has no effect on shade or light fastness and prevents staining of prints during washing-off treatments. The fixing effect of Erional FRN is stable even after heat setting and the treatment even protects polyamide fibres in subsequent thermal treatments.
Sarex Chemicals offers a range of moisture-management finishes for cotton, polyester and polyamide fibres. For polyamides Sarawick PSR imparts comfort, breathability, softness, moisture transport and a cool and pleasing handle. Sarawick PSR also meets the requirements of the Nike Wicking Test. Ultraphil PA from Huntsman Textile Effects, is designed for durable hydrophilic finishing of polyamide fibres and for soft handle finishing of polyamide fibres and their blends.
Ultraphil PA imparts increased wearer comfort through moisture transportation coupled with reduced static cling in garments. The good antistatic effects decrease problems in fabric cutting and sewing by allowing easier laying up, and separation/manipulation of the polyamide-fabric plies. Ultraphil PA has very good durability to washing and, on polyamide/cellulosic blends, aids improved resilience and shape recovery within resin-finished fabrics.
Fastness to chlorine is an important factor in dyed/printed polyamide/elastane swimwear. Hydrocol SCL (Rudolf Chemie) is an anionic formulation consisting of alkyl sulfonate and natural tanning agents. Hydrocol SCL has been developed for improving the fastness to chlorinated bath water and the wet fastness of dyeings/prints using acid/metal-complex dyestuffs on polyamide fibres, polyamide/elastane blends or polyamide microfibres.
This aftertreatment is normally carried out in a fresh bath set at pH 3.5-4.5, 60-70°C for 20 minutes. Applicable also via a pad-steam application, Hydrocol SCL does not affect the colour fastness to light, is resistant to hard water and improves the colour fastness to washing, perspiration, chlorinated water, water and sea water.
Huntsman Textile Effects has introduced Erional PCL, a cationic formaldehyde-free fixative applied via pad-drythermofix after dyeing to improve the colour fastness of reactive, acid and metal-complex dyes to chlorine without changing the shade. With good durability to washing, Erional PCL does not give rise to browning or yellowing of polyamide fabrics and also increases the wet-fastness performance.
Yellowing of fluorescent-whitened polyamide materials and discoloration of pastel-dyed polyamide and its blends during exposure to heat during processing (eg. moulding, pre- and post-dry heat setting) can give rise to considerable problems. Stabilon NY (Huntsman Textile Effects) is a special polyamide-fibre stabiliser that can be co-applied, and is compatible with most softeners and finishes. This cost-effective system is highly effective in small amounts, giving whiter whites and brighter shades, even under the extreme dry heat-setting conditions that are used to impart the highest standards of stability to polyamide garments.
References 1. N Bywater, Man-Made Fiber Year Book 2010, Chemical Fibers International, Oct (2010) 8.
2. Anon., Man-Made Fibre Yearbook 2010, Chemical Fibers International, Oct (2010) 11.