| 摘要 |
As a barrier film in a primary galvanic cell, use is made of a film formed from a water-insoluble alkali-soluble methyl cellulose having a methoxy content between 10 and 20 per cent. The thickness of the film may be between 0.0254 and 0.254 mms. The film may be cast from caustic soda solution and coagulated in a bath containing an acid and a salt, e.g. hydrochloric acid and ammonium chloride, or an acid salt, e.g. sodium bisulphate, any excess being subsequently removed by washing with water. In an example, to methyl cellulose having a methoxy content of 10.3 per cent is added boiling distilled water and the mixture is agitated to wet the fibres thoroughly. To this hot mixture 5 per cent aqueous sodium hydroxide solution is added and the resulting composition is stored at 0 DEG C. for 4 hours. A relatively clear fibre-free solution results. This solution is spread on a glass plate to a thickness of about 0.0508 mm. and the plate is immersed in an aqueous solution containing sodium bisulphate at 25 DEG C. for 10 minutes. Thereafter the film is peelled off the plate, washed in water at 45 DEG C. and air-dried to form a film of 0.0381 mm. thickness. Specification 603,927 is referred to. |
