CitationDownload as .RIS
Emerald Group Publishing Limited
Copyright © 2004, Emerald Group Publishing Limited
New polyamide dyes from Dystar
New polyamide dyes from Dystar
Keywords: Dyes, Polyamide, Materials
Polyamide is a versatile fibre that can be used in a wide range of applications: fashion garments, functional sports and leisurewear, ladies' hosiery, high-class lingerie, sewing thread, carpets, upholstery and even technical applications such as balloon and parachute silk, sails and automotive fabrics. Polyamide and polyamide fibre blends have a firm place in the women's and men's outerwear because they are easy-care and have good wear properties. The trend to functional textiles has increased demand still further. Sportswear is gaining ground in the fashion market and vice versa. Individuality and combinations of different fibres, fabrics and styles are in: high-heeled shoes worn with workout pants, outdoor jackets with mini skirts – a blend of fashion and functionality is all the rage.
Polyamide is increasingly being used in blends with natural fibres and other manmade fibres. Even more complex blends of three or more fibres, often including polyurethane, are now possible; dyeing and printing such fabrics is a real challenge requiring special processes and machinery. Expertise and the right dyes are therefore essential to produce economical results.
One starting material but many different types of fibre
A wide range of polyamide fibres is available, from ultra-fine microfibres containing fibrils of less than 1.0dtex, which are used in lightweight articles such as hosiery and lingerie, to coarse fibres of up to 2,100dtex for more robust articles such as suitcases, rucksacks and shoes. These days, round, trilobal and dumbbell cross-sections are most common. The number of filaments in the yarn varies enormously and it is this that determines the properties of the end-product. If different types of yarn are combined in a knitted or woven fabric, melange and bicolour effects can be achieved in one-bath dyeing processes. Similarly, the appearance of polyamide fibres can vary from high lustre to ultra-dull. Metallic-look fibres are the most recent trend and the latest yarn types allow all-over patterning rather than the less generous designs that were the characteristic of polyamide in the past. These yarns can be used in fashionable outwear, lingerie and sportswear and have led to a renaissance in printed swimwear and ultra-fine lingerie.
Consumers are becoming more demanding
Consumers expect increasingly high standards of wear comfort and functionality. They want garments that are breathable and transport perspiration away from the body. At the same time, they expect clothing to be water-repellent or even waterproof, resistant to UV light and have bactericidal properties. As with other fibres, there is a clear trend to higher fastness properties, especially high wash fastness for dark shades. In the past, washing at 30°C was considered sufficient. Now, garments are expected to be fast to repeated washing cycles at 40, 50 or even 60°C. That has greatly increased the use of metal-complex dyes in recent years. An investigation of the recipes used to dye sportswear showed that 10 years back about 20 percent of garments for this segment were dyed with acid dyes (Telon) which have a small molecular structure and only a minimal proportion were dyed with metal-complex dyes (Isolan) (Figure 1). These days, low-molecular- weight acid dyes are rarely found in sportswear collections. Instead, they are dyed with Telon A and M dyes, which have a larger molecular structure or with metal-complex dyes. Use of metal-complex dyes has grown fast and they now account for more than 40 percent of dyes used in the sportswear sector.
Rising quality standards accompanied by increasing cost pressure are a major challenge for the entire textile industry. Remaining competitive is therefore a key issue in the textile finishing industry and especially in polyamide dyeing. As the technological leader, DyStar is the ideal partner. DyStar's Controlled Coloration and Color Confidence programmes (Plate 2) provide for customers around the world high-quality products and service, innovations and technical advice to help optimise costs and raise quality.
The right colorants for all requirements
DyStar markets a full range of dye classes for polyamide and polyamide blends, from high- quality yet, economical standard dyes to innovative problem-solvers to meet top fastness requirements. The product range comprises dyes from the former leading suppliers Bayer and Hoechst, supplemented up by BASF's Acidol dyes, which are now marketed as Isolan 2S. In 2003, the range of dyes for polyamide was restructured to make it clearer and easier to use.
Isolan SP – the new all-round dyes for reliable dyeings and top fastness requirements
DyStar has developed the Isolan® SP range of dyes specifically to meet the demand for reliable all-round products that can be used in all dyeing processes. The core range of just four dyes covers a wide spectrum of medium to deep shades. They comprise special blends of 1:2 metal-complex dyes that ensure good coverage of barréness caused by differences in the structure of the material and have optimum exhaustion and levelling power even in sub- optimum conditions. These dyes therefore form the basis for Controlled Coloration of different polyamide qualities with a range of different dyeing procedures. Right-First-Time dyeing is standard with Isolan SP dyes. Since Isolan SP, Telon® M and Isolan S have similar exhaustion properties, they can easily be combined with one another. Isolan SP dyes are also a good illustration of the Color Confidence philosophy as there is no reduction in light fastness when they are applied in combination with acid dyes. Isolan SP dyes set new standards for on-tone dyeings on polyamide/elastane blends. Since there is virtually no staining of cellulosic and polyester fibres in blends, top fastness properties can be obtained on such blends. Moreover, Isolan SP dyes have very good wet fastness and light fastness properties and meet the specifications set by leading sportswear manufacturers. As well as Isolan SP dyes, DyStar markets a full range of acid and 1:2 metal-complex dyes to help customers meet wide-ranging demands in the coloration of polyamide.
Isolan 1:2 metal-complex dyes
DyStar markets three groups of metal-complex dyes: Isolan dyes are non-sulphonated products for pale to medium shades, for instance in the automotive sector. Isolan S dyes contain one sulpho group giving them the good wet fastness properties required for outdoor textiles, and Isolan 2S dyes with two sulpho groups can be used to obtain top wash fastness properties in heavy shades, for example in workwear.
Telon acid dyes
This product range is also subdivided into three groups: Telon dyes (monosulphonated, levelling dyes), which are mainly used for carpets and hosiery, Telon A dyes (monosulphonated half- milling dyes), which have good wet fastness properties and are commonly used in sportswear, and Telon M dyes (disulphonated milling dyes formerly marketed as Supranol dyes) with very high wet fastness properties for sportswear and swimwear.
Tried and tested processes for Controlled Coloration
Alongside the wide range of different articles and rising fastness requirements, textile finishers face another major problem: the dyeing behaviour of individual polyamide fibres can no longer be predicted accurately. The old rule of thumb that PA 6 took up dyes more quickly than PA 6.6 no longer holds. Changes in spinning and heat-setting processes have blurred the difference in dyeing properties. A reliable method of testing the dyeing behaviour of fibres is therefore becoming increasingly important.
To support its customers, DyStar has developed an unique test process, the Polyamide S process. This enables dyers to determine the exact behaviour of polyamide fibres in exhaust dyeing and make sure that the dyeing process is specifically tailored to their fibre and dyeing units. The Polyamide S process determines key fibre data (fibre saturation value and strike rate). These are then combined with data on the dyes. The result is a better understanding of the dyeing process and thus improved control.
The Optidye® N computer program is a logical development of the Polyamide S process. It uses known material properties and machine settings to calculate the pH, optimum concentration of auxiliaries, heating rate and shortest dyeing time. Optidye N is a good example of how Controlled Coloration can improve the quality of the goods and reduce process costs.
Polyamide and polyamide fibre blends have a firm place in womens outerwear because they are easy to care and have good wear properties. The appearance can vary from high lustre to ultra-dull.