Fabric finishing easy-care finishes

As a 1.7 dtex (1.5 den) fiber, it can be spun into yams with a better strength conversion factor than other ceUulosics, aUowing rotor-spun Tencel to outperform ring-spun cotton or modal viscose. Fabrics can be made at high efficiency, and prove to have the anticipated tear and tensUe advantages over other ceUulosics. Direct, reactive, or vat dyes can be used, and easy care properties can be achieved with less resin finish than normal. Tencel could therefore be positioned as a new premium quaUty apparel ceUulosic and not simply as a long-term replacement for viscose. 

Another category of durable hand builders are formaldehyde-containing thermosetting polymers. These products are usually supplied as dispersions or aqueous solutions of precondensates of urea or melamine with formaldehyde, for example di-methylol urea or di- to hexa-methylol melamine and their methyl ethers. The thermosetting polymers are comparatively inexpensive and provide fabrics with stiffness and resilience. However, they have a tendency to reduce abrasion resistance, yellow after exposure to heat, and release formaldehyde. Melamine-based hand builders are more highly crosslinked than urea-based products and are accordingly more durable. Butylated urea condensates are especially useful for rayon fabrics (see also Chapter 5 Easy-care and durable press finishes of cellulosics). 

Table 5.3 Importance of the requirements of easy-care finishes depending on the type of fabric ...

Textile chemical auxiliary suppliers will provide suggested recipes in their product information. These recipes will contain recommendations for the appropriate catalyst and other additives that improve the performance characteristics of the easy-care and dnrable press finishes, such as softeners to improve the fabric handle and prodncts to improve tear strength (for example polyvinyl acetate, amino-modified or epoxy-functional silicones). Less decrease in degree of polymerisation (DP) rating and abrasion resistance is provided by adding water-based poly-nrethane emulsions of self crosslinking silicone elastomers. 

A variety of test methods are nsed to evalnate the performance characteristics of fabrics treated with easy-care and dnrable press finishes. Some of the more common ones are snmmarised in Table 5.8. 

There are also serious side effects to fabric physical properties from flame-retardant finishing that must be recognised, often caused by the high application levels of the flame retardants. Harsh hand, loss of tensile suength and colour effects (fabric yellowing and dye shade changes) are common problems with durable flame-retardant finishes for cotton. The combination with other finishes, such as softeners, easy-care and repellent finishes, must be carefully tested. The flame retardancy of the multi-purpose finish is more often reduced than it is acceptable. 

Formaldehyde condensation products from urea and/or melamine are shown in Fig. 13.2. They are comparable to the corresponding products for permanent press and easy-care finishes (Chapter 5). They have the same advantages and disadvantages and they often improve the perspiration more than the washing fastness. Therefore they are mostly used for lining fabrics, where their price advantage is especially important. 

KAURIT M90 is used for the antishrink and easy-care finishing of cotton fabrics and spun rayons, for permanent fixation of calender effects, for the fixation of reactive filling and stiff finishes and for the stiff finishing of synthetic textiles, e.g., collar interlinings, petticoat fabrics, and lace. The product is often used in combination with other KAURIT or PIXAPRET types. 

Mercerization improves dimensional stability of cotton woven fabrics [63]. When knitted fabrics are compared with respect to their relative openness, temperature increases can be said to improve mercerization because when the goods are bleached and then mercerized, the fabric becomes more dense. However, when unbleached fabrics are mercerized, the fabrics become more open [64]. Mercerization also gives moderate improvement in crease recovery of cotton fabrics [65] as well as some protection against the decrease in tensile strength caused by easy-care finishing. 

Cellulosic fibres, especially cotton, are pretreated with alkali. After rinsing off, a certain amount of residual alkali usually remains in the fabric and this is often distributed unevenly. - This can lead to faults in subsequent processes where alkali interferes, for example with acid-catalysed finishes (easy-care, water-, oil-and soil-repeUent, stretch finish). Another problem caused by alkali is alkali spots. 

Table 6.8 shows the potential applications of biopolymers or their derivatives in imparting other functional properties such as insect-repellent, waterproof/breathable coating, hand building, easy care finishing/hand building to the treated cotton-containing fabrics. 

Easy-care finishing reduces the tendency of the fabric to crease in wear and makes it much easier to iron after laundering. It may also prevent shrinkage during washing. These types of finish have greatly reduced the maintenance which cotton and wool in everyday use require, and have increased their suitability for apparel of all types. However, there is a price for these advantages pollution. 

The easy-care treatment of cellulose fabrics uses padding with methylol-urea resins and curing them to cross-link inside the fibres. Consequently formaldehyde is the most important pollutant accompanying the easy-care finish. Alternatives were developed with resins without formaldehyde (reactive elas-tomere silicones, or dicarboxylic acids able to react with the OH groups of cellulose) but the results need still to be improved. Ammonia may also be used for improving the easy-care treatment in a mercerization-like process. This produces, on the other side, ammonia pollutants. 

Lately substitution of hazardous substances has become a hard task for fabric finishing companies. Substances such as easy-care products, fluorocarbons for water- and oil-repellent properties, various flame retardants (halogen or phosphor-based), plasticizers... 

Studies of lyocell fabrics processed with conventional open width techniques demonstrate the virtues of lyocell with low-cost production techniques and have shown the excellent easy care performance that lyocell can deliver in combination with resin finishing. The softness, fluidity and drape characteristics shine through even without fibrillation. 

Morley, R.J. and Taylor, J.M., Easy Care TENCEL Best Practice in Fabric Construction and Finishing , International Dyer 187, No. 4 1+, 5 pp., April 2002. 

Traditional easy-care finishing agerrts, such as dimethyloldihydroxylethylene-itrea (DMDHEU), can improve the surface appearance of textile materials, but as most are formaldehyde-related products, they will also weaken the fabric strength and prodirce harmful vapors. However, a liquid ammonia (LA) pre-treatment provides a soft hand feel, improves dimensional stability and increases the breaking strength of the treated fabric. However, it will not contribute to the sitrface appearance of fabrics. 

Shape memory polymer solutions or emulsions can be used as easy-care finishing agents on fabrics. The shape memory polymer layer on fabric can provide a recovery force during heating, which will result in a more flat appearance... 

In general, the properties of plastic-based synthetic fibers—most important among them being polyamide, polyester, and polyacrylonitrile— are essentially different from those of natural cellulosic and wool fibers, hence the sequence of finishing operations is likely to be different. For example, while cellulosic fabrics require a resin finishing treatment to impart easy-care properties, synthetic fibers already exhibit these easy-care criteria and require only a heat-setting operation. 

Sharing approximately the same proportion of EDA markets is the manufacture of polyamide resins, for hot melt adhesives and other uses, and ethylene bis(stearamide), used as a mold release agent. A small proportion of EDA is used to manufacture dimethylol-ethyleneurea resins for permanent-press and easy-care fabric finishes in the textile industry. The export market has occupied a substantial share of EDA production. 

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