| 摘要 |
Cellulose derivatives are made by treating cellulose with methyl, ethyl or other ethyl isothiocyanates in the presence of alkali. As starting material, there may be used bleached or unbleached cellulose or a material containing cellulose, hydrocellulose, oxycellulose or any alkali-insoluble conversion product of cellulose such, for example, as those obtained by mercerizing cellulose, or by treating the latter with strong mineral acids or zinc halide, or by heating with weak mineral acids, or by grinding in the presence of water. The cellulose may first be treated with aqueous or alcoholic solutions of alkali so as to form alkali cellulose which may be shredded and matured; or the alkali solution and the alkyl isothiocyanate may be applied to the cellulose simultaneously or successively in either order. The isothiocyanate may be diluted with ether, alcohol, etc.; and a small quantity of a copper, nickel or iron salt may be added as a catalyst. The reaction may be carried out without the supply of extraneous heat, or with heating or warming. The reaction product is dissolved in water or alkali, and the solution worked up into technical products; or the cellulose derivative may be isolated by washing the reaction product with water or aqueous alcohol optionally after neutralization or acidification, or alternatively by solution in water or alkali solution, and then by precipitating the cellulose derivative by the addition of an acid or salt to neutralize the alkali; the isolated product may be purified by solution in alkali and re-precipitating. The cellulose derivatives so obtained are generally soluble in aqueous alkali, and insoluble or sparingly soluble in water and organic solvents. The alkali-soluble derivatives are worked up into technical p products, such as:-artificial silk, cotton, wool, hair, straw, etc.; staple fibre; films; plates; plastic compositions; coating and layers; textile-finishing compositions, and compositions for dressing textiles, paper, leather, etc.; sizings for yarns; thickening-agents for pigments as in printing compositions; adhesive, cements, and binding-agents; book cloth; artificial leather; according to the application, the solution is brought to the appropriate shape or form, and is then acted upon by one or more coagulating agents. Suitable coagulating agents are acids, salts, alcohols, acetine, and in fact any coagulating bath known in the viscose art, in particular coagulating and plasticizing baths containing at least 35 per cent, preferably 50-80 per cent, of sulphuric acid or an equivalent amount of another strong mineral acid, as is described in Specifications 274,521, [Class 2 (ii), Cellulose &c.]; or the coagulation and plasticizing may constitute separate steps. Specifications 274,690 and 281,351, [both in Class 2 (ii), Cellulose &c.], also are referred to in the Provisional Specification. |
