| 摘要 |
Apparatus for the manufacture of films or sheets from solutions of cellulose esters or ethers in volatile solvents comprises a casting cylinder or the like enclosed in a chamber which is sub-divided into several compartments preferably four, in each of which one or more heating bodies such as radiators are provided and is characterized in that as the amount of solvent to be evaporated in the separate compartments decreases the radiators are arranged nearer to the casting surface of the cylinder. The cylinder may be replaced by a metal band or endless band provided with a suitable coating. In order to avoid stagnation of solvent vapours, the radiators in the first compartment are arranged at a considerable distance from the casting cylinder. In the second compartment where the proportion of solvent in the film is less than in the first compartment, the radiators are placed nearer to the casting surface thus effecting a greater heating of the film, but owing to the smaller quantity of solvent evaporated, the removal of vapour from the surface of the film is not impeded. If additional heating is required the temperature of the radiators may be increased. In the succeeding compartments, the radiators are arranged still closer to the casting surface so that the greatest heat is obtained in the last compartment before the film leaves the casting chamber. The last traces of the solvents may be removed by passing the film through a vessel containing hot or cold water. The film leaves this compartment coated with water vapour and thus the production of static electricity on the film is avoided. The evaporation of the water adhering to the surface of the film is effected automatically by the heat of the film itself or by a separate device. The solvents evaporated from the film may be recovered by condensation or absorption. |
