Metallic mordants

Many dyes that have no chemical affinity to fibrous substrates can be attached to such substrates by intermediary (go-between) substances known as mordants. These are either inorganic or organic substances that react chemically with the fibers as well as with the dyes and thus link the dyes to the fibers. Mordants are traditionally classified into two main classes, acid and metallic mordants. The acid mordants are organic substances that contain tannins (see Textbox 64) as for example, gall nuts and sumac. The metallic mordants are inorganic substances, mostly mineral oxides and salts that include metal atoms in their composition. Table 94 lists mordants of both these types, which have been used since antiquity. 

Mordant colouring matters dye wool or cotton in neither a neutral, nor an add, nor an alkaline bath, but act only in presence of a metallic mordant. 

The fiber is first treated with metal salts (mordanted). Highly adhesive, basic metal compounds are formed on the fiber. These compounds are capable of producing insoluble colored complexes (lakes) with certain azo and anthraquinone derivatives. Alizarin is the best-known anthraquinone derivative for this process (see Section 2.3). It used to be isolated from the root of the madder plant but has now been replaced by the synthetic product. Suitable azo dyes contain, e.g., hydroxyl or carboxyl groups in the position ortho to the azo group on one or both of the aromatic nuclei. The shade of the dyeing depends on the type of metallic mordant used. Alizarin with aluminum or calcium salts produces the well-known Turkey red. 

Salicylic and cresotinic acids are used in the preparation of azo dyes and of tri-phenylmethane dyes of the aurine type (eriochrome azurol B). These acids confer upon the dyes the property of going onto metal mordants, particularly chromium mordants, and also of forming complex compounds, in substance, with suitable metal salts. Salicylic acid is also widely used in the pharmaceutical industry. 

With this model of pseudomorph formation as a theoretical basis, it can be seen that the presence of large dye molecules, which can act as antioxidants or as blocks to fluid transfer, or the presence of metallic mordants, which can compete with copper ion, could be influential. Similarly, the impregnation of the fiber with other chemical species... 

This peculiar property of dyeing on metallic mordants has as yet had no satisfactory explanation. If cotton mordanted with alumina or oxide of iron is placed in an alizarin bath, the lake is precipitated and enters into intimate combination with the fibre. 

Acid dyestuffs, like alizarin c., are printed in the free state along with the metallic mordants (aluminium, iron, or chromium acetate) on steaming, acetic acid is driven off and the metallic oxide combines with the colour-acid to a firmly adhering lake. 

O.Ky- and amidocarbonic acids combine with diazo-compounds to form azo-dyes, some of which possess the property of dyeing on metallic mordants. 

Both may be dyed on metallic mordants, especially on iron or cobalt oxide. The mono-oximes, however, are more useful in this respect, and have for some time been applied technically. 

Euxanthone, although yellow, is not a dyestuff, while euxanthic acid is capable of dyeing on metallic mordants. 

Galloflavine is used along with metallic mordants. On alumina it produces a greenish-yellow shade, on tin oxide a pure yellow, and on chromium oxide an olive-green. It has been used to a slight extent in wool-dyeing on chromed wool it gives results similar to fustic. 

To make the colors bright and fast, natural mordants (an element which aids the ehemical reaction so that the fibre absorbs the dye, preventing the colour from either fading with exposme to light or washing out) sueh as Myrballams, rhubarb leaves, oils, minerals, alum, iron Vat, etc., are used. No heavy metal mordants like copper, chrome, zinc, tin, etc., have been used. 

Wenzel is said to have described the blue mass formed with cobalt oxide and alumina, afterwards called Thenard s blue this had been noticed by Gahn (see Vol. Ill, p. 201). The process was described by Chaptal, who says he initiated the research by Thenard and Merime. Thenard investigated the oxides and salts of mercury, phosphates of soda and ammonia, nickel, compounds (alloys) of antimony and tin, oxides of iron and other metals, mordants, a supposed black phosphorus, and phosphorous acid (which he found contained 100 phosphorus +110 39 seep. 60). He obtained... 

Uses Basic material for formulation of cleansing agents used in acid cleaners for metals and sanitation, highly alkaline degreasers, metal mordants antistatic effect Properties Colorless cl. liq. sol. in IPA, min. oil, benzene sol. cloudy in water sp.gr. 1.02 (20 C) vise. 200 mPa-s (20 C) pH 1.6 (10%) 100% act., 0.2% water Phosfetal 201 K [Zschimmer Schwarz]... 

Uses Basic material for formulation of cleansing agents, addle metal cleaners, alkaline degreasers, metallic mordants... 

Chemfac NC-0910 Chemfac PA-080 Chemfac PB-082 Chemfac PB-106 Chemfac PB-135 Chemfac PB-184 Chemfac PB-264 Chemfac PC-188 Chemfac PD-600 Chemfac PF-623 Chemfac PF-636 PEG Isodecyl ether phosphate Rhodafac BG-510 detergent, metal mordants Amphotensid D1 detergent, metal pickling Calsoft F-90 Igepal CA-720 Propetal 140... 

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