GB211178A - Improvements in dyeing - Google Patents

Abstract

Dispersions of insoluble mineral or half-mineral pigments, including bodies such as the heavy metal compounds of organic dyestuffs, for use as dye-baths, may be concentrated to reversible pastes in the presence of a large quantity of a semi-polar or amphoteric protective colloid, for example, gelatine, agar-agar or proteins. The dispersions should be as free as possible of electrolytes and are preferably homogeneous; to render them homogeneous they may be subjected to selective centrifugalization. Concentration may be effected by evaporation in vacuo, by centrifuging, by atomization in a sutable atmosphere or by electrokataphoresis. In an example of the preparation of a dye-bath for cotton, carbon, preferably obtained by the very slow combustion of an organic substance such as peat, is dispersed in a colloid mill, as described in Specification 155,836, in presence of a dispersator such as sulphite cellulose liquor, or a coloured body such as iron tannate or gellate, dividivi, Aleppo galls, algarobilla, logwood, extract of blue wood, or other substances which form lakes with alum, or with copper, cobalt, iron, chromium, or other salts. A number of other dispersions are also mentioned.ALSO:Materials, such as animal, vegetable or artificial fibres and fabrics, fur, feathers, cellulose esters, wood and paper, are dyed by immersing the material in a dye-bath containing a colloidal dispersion of an insoluble mineral or half-mineral pigment, including bodies such as the heavy metal compounds of organic dyestuffs, and coagulating the dispersion on the substrate. The use of a dispersion of an oxide of a metal of the iron group in dilute soap solution is specifically excluded. The coagulation may be effected physically for example by heat, ultra-violet light or electric current, or colloidochemically, such as by the addition of colloids of opposite polarity or of the same polarity but different intensity of charge, or by the addition of an electrolyte, particularly compounds of divalent or trivalent metals, or of an organic compound containing halogens, sulphur, nitrogen &c., for example sulphuric acids or heterocyclic compounds. In an example cotton is dyed with a dispersion of carbon preferably prepared by dispersing in a colloid mill, as described in Specification 155,836, [Class 1 (i), Chemical processes &c.], a carbon obtained from an organic material such as peat by very slow combustion, using as dispersator sulphite cellulose liquor or a coloured body such as iron tannate or gallate, divi-divi, Aleppo galls, algarobilla, log-wood, extract of blue wood, or other substance which forms lakes with alum or with copper, cobalt, iron, chromium or other salts. Lakes of alizarin or other dyestuffs may be added to the bath. The cotton is immersed in the dye-bath to which is added alum or other electrolyte and which is then heated to boiling. The goods may be brightened or otherwise improved by treatment with gelatine, agar-agar, gum arabic and tannin, aldehydes, alum &c. or with sulphonated fats or oils, drying oils, rubber solutions &c. Other examples show the dyeing of cotton in a bath containing ammonia, viscose, and colloidal ultramarine, iron oxide, or umber in the warm, or in the cold with the addition of an acid salt such as sodium bichromate, or bisulphate, alum or a double fluoride. Artificial silk may be dyed by this cold process. Wool, silk, hair, &c. are dyed in a bath containing colloidal carbon black, ammonia, albumen, casein or other protein, and resorcinol and may be after treated as in the first example. Cellulose acetate silk is dyed by treatment first in a bath of an emulsion of a solvent for cellulose acetate, such as chloroform or tetrahydronaphthalene, and then in a bath containing colloidal antimony sulphide, ammonia and sodium lysalbinate or protalbinates, and as coagulant an electrolyte, a heterocyclic compound, or a sulphonic acid, for example of a fatty acid ester, phenol, naphthene or terpene. Paper is dyed in a bath of colloidal cinnabar and ammonia or sodium sulphide, and the colour is coagulated in a faintly acid solution of gelatine. Leather is dyed in a bath of colloidal carbon black, linseed oil and water. The dispersions for the dye baths may be freshly prepared or may be made by diluting pastes obtained by concentrating dispersions with a large amount of a protective colloid such as gelatine, agar-agar or proteins, the amount of electrolyte present being small. The dispersions are preferably made homogeneous by selective centrifugalization. The concentration may be effected by evaporation in high vacua, by centrifuging, by atomization in a suitable atmosphere, or by electrokataphoresis. One of the Provisional Specifications also refers to the use of these concentrates for textile printing.