| 摘要 |
A plasticized cellulose acetate composition suitable for the production of wrapping films comprises 65-90 per cent. by weight of cellulose acetate and, as a plasticizer therefor, 5-25 per cent. by weight of a mono-phenyl ether of a polyethylene glycol containing 4-6 oxyethylene groups and from 0-17.5 per cent. of a solvent plasticizer for the cellulose acetate, the sum of the mono-phenyl ether and the solvent plasticizer being 10-35 per cent. of the composition, and the mono-phenyl ether being at least 50 per cent. of that sum. The composition may be formed into wrapping films which are permeable to water vapour. The additional plasticizer may be dimethyl or diethyl phthalate, dibutyl tartrate, tricresyl phosphate or methyl phthalyl ethyl glycollate. Dyes, pigments and volatile solvents, may be incorporated with the composition. The cellulose acetate may have an acetyl content of 37-42 per cent. For producing a film-casting solution, the cellulose acetate may be dissolved in a mixture of methyl ethyl ketone, ethyl acetate, dioxane and acetone to form a stock solution, and to this may be added the plasticizer or mixture of plasticizers in the appropriate proportions. If desired the plasticizers may be incorporated with the cellulose acetate by mixing on hot rolls and the molten mass may be cast as a film on a moving belt or may be extruded through a slit. Alternatively, a viscous solution of cellulose acetate and plasticizers in a volatile solvent may be prepared and then extruded into an evaporative atmosphere. |
