**1. Introduction**

240 Textile Dyeing

Lyocell fibres display a higher tendency to fibrillation compared with other cellulosic fibres because they have a higher degree of crystallinity on the fibre length (90% for Lyocell, in contrast with 60-70% for viscose fibres). In order to remove the primary fibrillation, in washing, whitening or dyeing, it is necessary to apply enzymatic treatment with the use of special cellulasic enzymes. Enzymatic treatment, doubled by a controlled mechanical action, lead to a complete and of long duration defibrillation. Bio polishing after dyeing results in

 Products with enhanced functionality are important to survive the competition New Processing concepts have to be adapted in order to be able to produce short

Adequate steps must be taken by the textile industries for the optimum utilization of energy and water resources. The textile industry is expected to play an ever-more-progressive role in developing environmentally friendly technologies and processes. Training the employees and creating awareness among them regarding the importance of water and energy conservation is also essential. There is a lot of potential for savings. By saving on the energy and water resources, textile industries can not only save on the costs, but can also help to

The textile industry is aware of the decrease in water sources and they are developing new technology and new chemical alternatives, but the challenge will lay in converting the technology in current textile facilities into the new technology that uses less water. Another challenge lays in changing the mindset of the current generations in the textile industry to use the new chemical alternatives instead of the chemicals they have used in the past decades. This will be a slow process, but one that will need to happen in order for the textile

[2] Rossari Biotech Ltd -Internal Document for Circulation on Pre-treatment of Cotton

[3] Lecture on Sustainability - Textile Processing - By Mr Edward Menezes during

[4] Article by Edward Menezes on Water Pollution and measures to reduce it- part 1,

[5] Rossari Biotech Ltd -Internal Document for Circulation on Scourenz ABE Liquid [6] Rossari Biotech Ltd -Internal Document for Circulation on Koolwhite 2020 Liquid

Workshop on Physico-chemical Aspects of textile fibres , Dyes, and Polymers at

 New processes offer the opportunity to fulfil the needs of the customers Reducing environmental impact will help textiles processors save resources Reduces water and energy use versus conventional high-temperature processes.

industry to maintain current production and grow in the future.

ICT on 15th October 2010, Matunga Mumbai

Colourage June 2010- page nos 73-78

colour loss, so it is preferred before dyeing.

Processes, environment and products

**9. Concluding remarks in general** 

In textile focus should be on

batches

**10. Conclusion** 

**11. References** 

slow down the climate change.

[1] http://www.rossari.com/tech.asp

Processing -Surat part 1

Plasmatic double barrier discharge (DBD) obtained in air at atmospheric conditions is widely used, among other non-thermal plasmatic alternatives, to modify chemical and physical properties of different textile polymers (Morent et al., 2007).

The impacts of DBD on environmental aspects of textile processing rise to get high attention due to important reduction of costs in dyeing by savings in processing times, products, human resources, water and energy (Carneiro et al., 2001). All fibers, from natural to synthetics, can be submitted to several irradiation methods with diverse and significant meaning in different areas of textile processing (Sparavigna, 2001).

The effects on surface are reported for cellulosic fibers (Carneiro et al., 2005; Souto et al., 1996), wool (Rakowski, 1992), polyester (Oktem et al., 2000, Leurox et al., 2009), polyamide 6.6 (Papas et al., 2006; Oliveira et al., 2009), polyamide 6 (Dumitrasku & Borcia, 2006), polytetrafluoroethylene (Liu et al., 2004), polyethylene (Oosterom et al., 2006), polypropylene (Yaman et al., 2009) and meta aramid (Chen et al., 2008), being roughness, microporosity and creation of polarity by oxidation mechanisms the main modifications induced by several types of irradiation techniques.

Acid dyes are the most common in use for polyamide dyeing, but some problems are very well known, as difficulties to manage uniformity and fastness. The necessary pH to achieve a good exhaustion of dye in the fiber must be carefully controlled and sometimes is excessively low.

Reactive dyes are very important for the dyeing of cellulosic and protein fibers, but in polyamide the results are not equivalent due to paler colors obtained (Soleimani et al., 2006). Reactive dyes for cellulose are similar to acid dyes in their chromophoric structure, but they possess reactive groups able to react chemically with the fiber in the presence of alkali. Only few of these dyes have been developed for polyamide application with ability to react with amino groups in fiber structure without the need of alkaline fixation. Stanalan (Dystar) and Eriofast (Ciba) are well known dyes for this purpose.

Reactive dyes for cotton fibers, Procion (Dystar), Kayacelon (Nippon Kayaku), and Drimarene (Clariant) were tested for polyamide dyeing at boiling temperature and different pH showing distinct results. At pH 4, the most convenient result was obtained due to a high protonation of nucleophilic amino groups, contributing to electrostatic attraction between anionic dye and positively charged fiber (Soleimani et al., 2006).

Polyamide 6.6 Modified by DBD Plasma Treatment for Anionic Dyeing Process 243

A double barrier discharge was produced in a semi-industrial machine (Softal/University of Minho) functioning with air at normal temperature and pressure, using a system of ceramic electrode and counter electrode with 50 cm effective width, and producing the discharge at

The power of discharge, velocity, number of passages of the fabric between electrodes were variable corresponding to calculated discharge dosages from 400 to 3600 W.min.m-2

*W P Dosage V L*

Equation 1. Plasma dosage determination, where W = power (Watts); P = number of

**Power (W) Velocity (m**.**min-1) Number of passages Dosage (W**.min.m-2) 500 2.5 1 400 1000 2.5 1 800 1000 2.5 2 1600 1500 2.5 1 1200 1500 2.5 2 2400 1500 2.5 3 3600

In order to evaluate the wettability of the untreated and of the plasmatically modified polyamide woven fabrics, a water-drop test was applied by measuring the time for its

(1)

High voltage electrode

High voltage electrode

(Table 1). The dosage was calculated according to the following equation (Eq.1):

passages; V = velocity (m.min-1) and L = width of treatment (0.5m).

Table 1. Experimental parameters of DBD plasma and dosage applied.

**2.3 Characterization of DBD treated fabrics and structural analysis** 

**Acid dyes** - Telon Blue MGWL, Telon Red A2FR and Rot M-6BW.

All of them were kindly supplied by Dystar ®.

**2.2 Plasma treatment 2.2.1 DBD plasma machine** 

high voltage and low frequency.

Fig. 1. DBD plasma machine diagram.

**2.3.1 Water drop absorption test** 

complete absorption into the material.

**2.2.2 Plasma dosage** 

In order to achieve better dyeing results in polyamide fibers some trials are reported in the bibliography using new techniques for structural changes, being irradiation by means of lasers and plasmas presented as promising solution.

Low temperature plasmas via several gases such as oxygen, tetrafluormethane and ammonia were used for modification of fibers i.e. wool and polyamide 6. Dyeing of modified fibers was performed with several natural dyes and the dyeing rate of the plasmatreated wool was considerably increased (Wakida et al., 1998).

Polyamide 6 was treated with tetrafluoromethane low temperature plasma and then dyed with commercially available acid and disperse dyes. Acid dyeing results show that this type of plasma treatment slows down the rate of exhaustion due to an increase in hydrophobic groups at the surface originated by the type of gas used, without reduction of the amount of dye absorption at equilibrium.

The dyeing properties of disperse dyes on plasma-treated polyamide fabrics markedly increase comparing with untreated fabric by increasing hydrophobic attraction between disperse dye and the fiber (Yip et al., 2002).

Polyamide 6.6 fabric was dyed with a disperse-reactive dyestuff and a covalent bonding with the fiber was proved to occur if supercritical carbon dioxide is used (Liao et al., 2000).

Polyamide 6 materials irradiated with 193 nm ArF excimer laser developed micro-sized ripple-like structures on the surface, able to increase surface area and light diffuse reflection. Laser treatment is proved to be responsible by breaking the long chain molecules of polyamide resulting in an increase of amine end groups' content. Results revealed that dyeing properties of reactive dyes tested on polyamide fabrics improve after this treatment, in what concerns both kinetics and equilibrium phases (Yip et al., 2004).

In the present work, polyamide 6.6 fabrics were treated with different dosages of an atmospheric double barrier discharge obtained in a semi industrial prototype equivalent to an industrial machine installed in a Portuguese textile plant [Pat. PCT/PT 2004/ 000008(2004)]. The structural and chemical modifications of fabrics were further analyzed in terms of X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) techniques. Moreover, the tinctorial behavior (color strength, exhaustion) of the polyamide fabric dyed with different dye classes, namely reactive dyes for wool, reactive dyes for cotton, acid and direct dyes, was studied as well as washing and rubbing fastnesses.
