Sodium acetate fibres

Basic colouring matters are those the solutions of which are decolorised by mineral acids and give a coloured precipitate with tannin (best in presence of sodium acetate). When acidified with sulphuric acid and shaken with ether, their solutions give up nothing to the solvent. They dye animal fibres in a neutral bath or one faintly acid with acetic acid, without a mordant, and they dye cotton in a tannin bath. Mineral acids remove them completely from the fibres on which they are fixed. 

Bleaching of acetate fibres with sodium chlorite... 

It is more safe to carry out bleaching of acetate fibres with sodium chlorite than with hydrogen peroxide. Bleaching can be carried out with sodium chlorite (0.5-2 g/1) in presence of mono substituted ammonium phosphate (0.5-2 g/1) and non-ionic detergent at 70-80 C for 60-100 min. 

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. 

It should be noted that regeneration of acetic acid fi om sodium acetate is of certain practical interest, since sodium acetate is formed as a by-product in the manufacture of synthetic fibres. A 10% solution of sodium acetate is placed into the central compartments of the electrodialyzers. The anode compartment is filled with 0.1 N sulfuric acid solution and the cathode compartment with 0.1 N caustic soda solution. The electrodes are made of platinum, and the current density is 6.5 A/dm. ... 

Non-destructive partial stripping techniques for basic dyes on acrylic fibres are carried out at 100 °C (or higher if possible) using, for example, 1-10% o.w.f. anionic retarder and 1 g/1 acetic acid (60%), or 1-5 g/1 Marseilles (olive oil) soap. Destructive stripping requires acidified (pH 5.5-6.0) sodium hypochlorite, followed by an antichlor treatment in sodium dithionite or sodium bisulphite. In some cases a preliminary boiling treatment in 5 gA monoethanolamine and 5 g/1 sodium chloride is said to improve the effect of the stripping treatment. 

This term was originally intended to denote all kinds of man-made textile fibres, but is now applied only to cellulose types. Viscose rayon (regenerated from a solution of cellulose xanthate in sodium hydroxide) accounts for the greater part of world rayon production. Acetate rayon and cuprammonium rayon are relatively unimportant. 

If it is not possible to select dyestuffs which will give a solid result on both fibres, it is necessary to dye in the presence of 4 to 8 per cent of carrier until the polyester is on shade. The polyamide is then stripped with sodium hydrosulphite or zinc formaldehyde-sulphoxylate and acetic acid at the boil, leaving the other fibre unaffected because, on account of its hydro-phobic nature, the entry of the hydrosulphite into the polyester is extremely slow. It is, of course, important to select dyestuffs which will reduce easily to colourless compounds. The nylon can then be dyed to... 

The acrylic component can be left undyed quite easily because it has no affinity for those direct dyes which are classified as acetate reserving. There are also many diazotized and developed direct, as well as vat dyes which will dye the cellulose only. Disperse dyes can be used for acrylonitrile fibre, but they will stain the cotton or rayon component, and clearing with a solution containing 8 oz to 1 lb of potassium permanganate and 2 oz of sulphuric acid per 100 gallons at 30 C (86 F) for 15 minutes, will probably be necessary. The oxides of manganese will subsequently have to be removed with sodium bisulphite. 

Disperse dyes are not suitable because the polyamide is dyed much more heavily than the acrylic. The cationic dyes can be applied with 5 per cent of Glauber s salt at pH 4-5 adjusted with acetic acid, at the boil. The polyamide will only be slightly stained, if at all. The latter fibre can be cleared, if necessary, with potassium permanganate and glacial acetic acid (1 lb and 2 oz per 100 gallons respectively) at 25 C (77°F), followed by treatment wdth. sodium bisulphite. 

The dyed material is sewn between two pieces of doth of the same fibre. The test solution contains 1 g of sodium chlorite (80 per cent) per litre and, before the test, sufficient acetic acid is added to bring the pH to 3 5. The specimen is wetted out in the solution and subsequently immersed in it at 80 2°C (176 4 F) for 1 hour, using a liquor ratioof 50 1. The sample is then washed in cold running water for 10 minutes and dried at a temperature below 60 C (140 F). 

Fixation of the mordant The fixation is mostly achieved by drying of the textile at low temperature. Kiel showed that the formation of Al(OH)3 out of aluminium acetate mordant and sulphonate mordant is essential for the fixation. He demonstrated that the deposition of Al(OH)3 in the fibres was maximal if the pH lies between 4 and 9 during the fixation. At pH < 4 or pH > 9 the Al(OH)3 dissolves again. Kiel found that fixation of the textile at 40°C for 30 min or 1 min at 70°C in 3 ml sodium silicate solution (or 10 g chalk/L) are the best conditions [20]. 

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