Patent GB-403944-A (GB)
Title: Improvements in the manufacture or treatment of pigments and of textile materials, films and the like containing such pigments
IPC: D01F1/10
Filed: 1932-06-23
Abstract: Wet inorganic pigments are dried by contact with hot vapours of organic substances.  The dried pigments are incorporated in the solutions from which are obtained artificial threads, films, and the like, or are applied to artificial textile materials, or films subsequent to their production.  When pigments which have been dried in this manner are employed, there is less tendency for the materials to cut the guides or other portions of the apparatus with which they come into contact.  The pigments may be incorporated with spinning solutions of cellulose acetate or other cellulose organic ester, or cellulose nitrate, or a cellulose ether, or viscose, or cuprammoniumcellulose.  The pigments may be white or coloured.  The sulphates, and carbonates of barium, calcium, and lead; oxides and hydroxides of titanium, zinc, antimony, aluminium and tin; phosphates of tin and barium; carbonates of zinc and magnesium; borates of calcium and barium; chromates of barium and lead; cadmium sulphide, Prussian blue, cobalt yellow, iron red, chrome red, blue verditer, Schnitzer's green, manganese brown, and Vandyke brown, are specified. The process may be applied to pigments obtained by precipitation from solutions.  The organic substance which is to be vapourized and passed over the wet pigment, may be a water immiscible compound such as a mineral or vegetable oil, xylene, anthracene, diphenyl, diphenyl ether, iso-amyl benzoate, benzyl benzoate, amyl stearate, polyglyceryl acetate, tricresyl or triphenyl phosphate, acetanilide, oxanilide, or ethyl glycol phthalate.  The organic substance may be partially miscible with water and may be capable of forming an azeotropic mixture.  Examples of partially miscible liquids are:--ethylene and trimethylene glycols, glycerol, benzyl alcohol, cyclohexanol, di- and tri-acetins, tri-butyrin.  The treatment may be carried out at the boiling point of the organic substance or at higher temperatures and if desired at higher pressures.  The organic vapour may be mixed with air or inert gas. A mixture of two vapours may be employed, the substance of lower boiling point being capable of forming an azeotropic mixture with water while that of higher boiling point tends to remain with the pigment particles.  In some cases such as the treatment of antimony trioxide, liquids of comparatively low boiling points such as methyl alcohol, acetone, methyl acetate, or methylene chloride may be used.  The dried pigments may be further ground before or during their incorporation into the solutions from which threads or films are obtained.  They may be incorporated directly into the spinning solutions or incorporated in another liquid which is then dispersed in the spinning solution.  The threads obtained have a modified lustre or are coloured.  When the pigments are applied to artificial threads after their formation it is preferable to treat the textile material with a swelling agent.  In an example, wet precipitated titanium hydroxide is spread in thin layers on trays in a drying chamber through which are passed hot vapours of anthracene and olive oil until the pigment is dried.  In another example, vapours from a hot mixture of diphenylether and diethylene glycol are passed through freshly precipitated zinc sulphide until the pigment is dry.  The Provisional Specification describes the removal of other liquids than water from pigments, the dehydration of aluminium hydroxide with production of alumina, and the dehydration of colloidal or finely divided metals.