Improved wet fastness

Properties provided by these finishes are mostly improved wet fastness, for example washing, water, perspiration and ironing fastness, then better light fastness and only to a small extent improved crocking and rubbing fastness. For other kinds of colour fastness, for example dry ironing, chlorine, peroxide and carbonisation, there are no known possibilities for improvement by an after treatment. The market importance of these finishes is based on customer preferences and economic production demands. For abetter understanding, each of these three quite different fastness improvements will be dealt with separately. 

Another approach for removing reactive dye hydrolysates from the fibre and from the wash water (decolourised waste water) is the use of peroxidases (oxidative active enzymes such as Baylase RP). This multipurpose enzymatic rinse process saves time, energy and water but it is restricted mainly to jet applications. The question of the potential toxicity of the resulting aromatic nitro-compounds (cleavage products of the reactive azoic dyes) has to be resolved. 

Another solution to the problem is the reactant fixation of the dyestuffs to the fibre with highly reactive uncoloured chemicals. Their main problem is their essential high reactivity, which causes cancer or mutagenicity when they come into contact with the finish workers. The end user is not involved because after the fixation reaction these chemicals lose their risk to health. 

An older method of improving the wet fastness of selected direct dyeings is their diazotisation on the fibre, followed by the reaction with so-called developers 

1 Quaternary ammonium polymers improve wet fastness with anionic dyes. 

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The fact that the aftertreatment of direct dyes has a long history is not surprising since wet fastness within this class is not particularly good. Their prime advantages are ease of application and economy compared with dyes of higher fastness (reactive, sulphur or vat) -hence the continued search for highly effective aftertreatments that improve wet fastness... 

The progressive introduction of methyl groups into the pendant phenyl ring of Cl Acid Blue 25 (6.30 R = H) leads to an increase in dye uptake and to improved wet fastness properties on wool [12]. Steric crowding in the case of Cl Acid Blue 129 (6.33) reduces the conjugation of the 4-substituent with the remainder of the system and results in a reddish blue hue. The aliphatic cyclohexyl ring in Cl Acid Blue 62 (6.31) has a similar effect on the hue. 

This versatile water-soluble reactant has been evaluated in wool and nylon dyeing. The nucleophilic aminoalkyl derivatives of orthodox aminochlorotriazine dyes behave like traditional acid dyes on wool owing to their zwitterionic character under neutral-dyeing conditions (Scheme 7.65). Improved wet fastness can be achieved using the reactant XLC... 

Much research work has been done and continues to be done on the development of new dyes for this outlet. For instance, Avecia have a range of yellow magenta and cyan dyes, based on the ammonium salt principle above, which do show improved wet fastness properties. An alternative approach adopted by workers at Ilford, based on their experience in colour photography, involves the molecular tailoring and formulation of dyes which aggregate and hence have light fasmess properties nearer to pigments (Archiva Inks). 

Precursor of the formaldehyde condensation polymer that improves wet fastness on cellulosic fabrics. 

Reaction products of formaldehyde and aromatic sulfonic acids (syntans) improve wet fastness on nylon. 

Some potential problems with finishes designed to improve wet fastness include ... 

References concerning finishes that improve wet fastness... 

Fixing agent for improving wet fastness properties of pigment prints. 

POMOFIX VK 75 is a non-formaldehyde containing resinous aftertreating agent used to Improve wet fastness of direct, develop, and fiber reactive dyes on cotton and rayon. 

Solid shades on unions with improved wet-fastness are dyed with mixtures of acid dyes and direct dyes capable of forming complexes with... 

A single-bath method can be used if desired. The dyes are dissolved separately and added to the dyebath which already contains an ethylene oxide condensate which acts as an anti-precipitant. The dyebath is adjusted to pH 5 to 5-5 with acetic acid and sodium acetate and the goods are entered at 40 to 45°C (104 to 113°F). A period of 45 minutes is taken to raise the temperature to the boil, at which it is maintained for one hour. Alternatively, the acrylic fibre may be dyed first and then the same liquor is neutralized and the cellulosic fibre is dyed. Application of a cationic fixing agent improves wet fastness of direct dyes but copper after-treatment should be avoided because this can have an adverse effect on the light fastness of the cationic dye. Very good fastness is obtained if, after the acrylic component has been dyed, the cellulosic fibre is brought to shade with vat dyes. 

Mordant. This class is now restricted to that group of special wool dyes, the dyeings from which are treated with aqueous bichromate in order to improve wet fastness. This treatment may be apphed to the fabric before dyeing, during the dyeing process or afterwards. Application after dyeing or after chrome process is the method most widely used. 

Uses Fixing agent for textile Industry Improving wet fastness props, of direct and reactive dyes on cellulosic fibers Properties LIq. 

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