GB371604A - Improvements in and relating to envelopes for gas cells - Google Patents

Abstract

Cellulose carboxylates, nitrates, and ethers.--Envelopes for gas cells consist of one or more layers of an organic cellulose derivative or derivatives soluble in organic solvents and one or more layers of a highly polymeric albuminous compound or compounds, such as gelatine, glue, or casein. For small gas cells, e.g. meteorological testing balloons, layers of these kinds are sufficient, but for larger gas cells, as in aircraft, textile web is incorporated. The web may be coated with solutions of the materials, or applied to the surface of the composite film while this is softened by heat or by a solvent or swelling agent; or the web may first be combined with a prepared single layer and then coated with a solution, or first coated with a solution and then combined with a solid sheet. It may thus be provided with impervious coatings on both sides, or several coated webs may be combined. Suitable cellulose derivatives are esters and ethers such as cellulose acetate, acetate-butyrate, laurate, or butyrate-laurate, ethyl cellulose laurate, ethyl cellulose, benzyl cellulose, and hydroxy-alkyl celluloses and their esters. These preferably preponderate in the composition of the compound film. softening agents, natural or artificial resins, filling materials, colouring agents, fireproofing substances, or the like, may be added to the materials. In an example, 45 grm. of cellulose acetate are dissolved in 255 c.c. of a mixture of 9 parts acetone, 1 of ethanol, and 1 of benzene, and to the solution are added 40 c.c. of a condensation product of acetaldehyde and glycerine and 23 c.c. of a solution of gelatine (0,5 per cent) in a mixture of 2 parts of water, 1 of methanol and 1 of acetone. A film formed from this solution is coated with a 10 per cent solution of gelatine in aqueous acetone, to which glycerine to the amount of 30 per cent of the gelatine has been added. After drying, another film of the first kind, or an ordinary cellulose acetate sheet, is applied. The composite film is softened with acetone and pressed on to the web. Cotton fabric may be placed between the gelatine layer and the second cellulosic layer. According to the Specification as open to inspection under Sect. 91 (3) (a) the cellulose derivative may be the nitrate. This subject-matter does not appear in the Specification as accepted.