Patent GB-316521-A (GB)
Title: Improvements in the treatment of materials containing cellulose esters
IPC: D01F2/28
Filed: 1929-07-29
Abstract: 316,521. British Celanese, Ltd., (Assignees of Dreyfus, C., and Schneider, G.). July 28, 1928, [Convention date]. Yarns, treating with liquids.-Yarns made of organic esters of cellulose, for example, cellulose acetate, formate, propionate or butyrate or mixtures thereof or containing one or more organic esters of cellulose mixed with other fibres, for example, cotton or silk, are saponified by applying over the whole surface of the material a paste containing an alkaline saponifying agent, for example, caustic soda, caustic potash, sodium or potassium carbonate or, silicate or trisodium phosphate, and immediately drying the material under the influence of heat, for example, in a drier or on heated drums. The material may thereafter be steamed. The paste may be applied in any desired manner, for example, by printing, pin, padding or all engraved rolls or by brushing or spraying. Any suitable thickening agents which are sufficiently resistant to the alkaline saponifying agent may be added to the paste, for example, gum tragacanth, gum tragasol, dextrin, British gum, water soluble cellulose ethers, starches, particularly potato starch, gum arabic or mineral thickening agents, such as Fuller's earth or infusorial earth. Materials treated in this manner possess higher safe ironing temperatures. By adjusting the conditions of treatment, the saponification may be rendered purely superficial, but the depth to which saponification takes place may be controlled by addition to the paste of buffer salts or modifying agents such as soap, sodium acetate, or borax or of swelling agents for the cellulose derivative, such as ethyl alcohol. Materials superficially saponified in this manner retain their affinity for dyestuffs customarily applied to cellulose acetate, for example, the dispersed insoluble or basic dyestuffs, and at the same time acquire an affinity for cotton colours, such as the substantive or direct cotton dyestuffs. Differential or uniform efforts may be obtained by applying such dyestuffs to the treated materials. Alternatively, dyestuffs having an affinity for cotton and not affected by the saponifying agent may be incorporated in the saponifying paste. Discharge effects may be obtained by the use of dischargeable colours and by applying suitable discharging agents. In an example, a woven fabric consisting wholly of cellulose acetate is treated over the whole of its surface with a paste comprising caustic soda, water, and gum tragacanth or British gum or gum arabic. The paste is applied on a printing machine, for example, by means of a pin or all engraved roller, and the fabric is passed immediately over drying drums and then steamed for 20 minutes with steam at 5 pounds pressure. For the production of discharge effects, dischargeable dyestuffs may be applied and discharging agents thereafter applied locally, for example, by means of engraved or embossed rolls, plates, or blocks, or by brushing or spraying through stencils. The discharge paste may contain any suitable reducing agent, for example, sodium hydrosulphite, sodium formaldehyde hydrosulphite, zinc hydrosulphite, or zinc formaldehyde sulphoxylate. Dyestuffs resistant to the discharge agents may be incorporated in the discharges to obtain coloured discharge effects. For white discharge effects the sodium hydrosulphite for formaldehyde hydrosulphite is preferred while for coloured discharges zinc formaldehyde sulphoxylate is preferred. The Specification as open to inspection under Sect. 91 (3) (a) refers: to the local application of the pastes. This subject-matter does not appear in the Specification as accepted.