| 摘要 |
Water-insoluble and mustard-gas resistant films and coatings are made by acetalising a film or coating of polyvinyl alcohol by treatment with an aqueous solution containing an aldehyde, an acid catalyst and sufficient of a non-solvent for polyvinyl alcohol to render the aqueous solution non-solvent, the acetalisation being allowed to proceed only to the stage at which the film becomes insoluble in boiling water. Aldehydes include formaldehyde, acetaldehyde, benzaldehyde, acrolein and furfural. Catalysts include hydrochloric, sulphuric, nitric and phosphuric acids and sulphur chloride. Non-solvents include acetone, dioxane and methylene ethylene ether. Coatings of polyvinyl alcohol on woven fabrics of cellulose or regenerated cellulose yarns, wood, leather, paper, fibre-board or asbestos or films bonded to the base under pressure, preferably in the presence of glycerine or glycol, may be treated. The flexibility of the treated film may be retained by coating with glycerol or calcium chloride or by forming on both surfaces a layer of a water-insoluble soap, e.g. sodium oleate, stearate or palmitate. In an example, the partially acetalised film is immersed in an aqueous solution of ammonia and acetone to remove residual aldehyde or acid and then in an aqueous solution of sodium oleate followed by aqueous calcium chloride to deposit a water-insoluble soap on both surfaces, rinsed with acetone and dried. The product may be used for making wearing apparel, packaging material and piping. |
