GB388387A - Improvements in the manufacture of moulded articles from cellulose derivatives - Google Patents

Abstract

Relatively smooth thin sheets, films, foils, &c. containing thermoplastic derivatives of cellulose such as cellulose nitrate, acetate, &c., and cellulose esters, are made by kneading such a derivative with solvents, plasticizers, &c., obtaining a plastic mass containing only a small proportion of solvent, say 1-3 per cent, and forming the films &c. by extrusion of such mass through a shaped orifice or by passage between calendar rolls. The process may be carried out as follows: The cellulose derivative together with plasticizers, solvents, &c. are first kneaded, then filtered, and next transferred to vacuum kneaders for the removal of excess solvent; the stock is then worked on mixing or converting rolls until homogeneous and of the desired solvent content, in some cases the whole of the solvent being removed; when the material on the malaxating rolls is homogeneous, it is finally passed through as a very thin sheet, and is then smoothed and rendered uniform in thickness by passage through one or more pairs of calendar rolls; residual solvent in the film may be removed by passage over a series of heated rollers or by passage through festoon driers, and the completed film may be rolled up or cut into sheets. When the extrusion method is employed, the extruding machine may be made a part of the equipment for filtering the plastic mass; and the extruded film may be received on a belt or wheel, and it may be passed through calendar rolls. The several stages of the process, including the extrusion step when such is used, may be carried out as a continuous operation. The film, which is particularly suitable for the manufacture of laminated glass, may be used directly, while preferably containing a small percentage of solvent, for such manufacture without the necessity for the application of coatings to the glass, the film after any required treatments such as the application of adhesive, cutting into sheets, &c., being applied directly to the glass sheets which may be carried by an endless band; subjection to heat and pressure secures the sheets together and also completes the homogenization of the cellulose ester &c. The material is also suitable for the manufacture of imitation pearl, wood heels, and toilet sets. The Specification as open to inspection under Sect. 91 refers to the production of moulded articles; to the production of incompletely converted sheet material, the conversion to be completed when the article is moulded; and to the production of moulding powders particularly of cellulose acetate, by pulverizing the incompletely-converted brittle sheets. This subject-matter does not appear in the Specification as accepted.ALSO:Thermoplastic cellulose derivatives such as cellulose nitrate, acetate, &c. and cellulose ethers, are kneaded with solvents, plasticizers, &c., then filtered and next transferred to vacuum kneaders for removal of excess solvent; the stock is then worked on mixing or converting rolls until homogenous and until the solvent content is reduced to 1-3 per cent, or in some cases the solvent is entirely removed. The material is then converted into sheets by passage between calendar rolls or by extrusion through a shaped orifice; or the material is used for the manufacture of imitation pearl, wood heels, and toilet sets. The Specification as open to inspection under Sect. 91 refers to the use of the material for the manufacture of moulded articles; to the production of incompletely converted sheet material, the conversion to be completed when the article is moulded; and to the production of moulding powders particularly of cellulose acetate, by pulverizing the incompletely converted brittle sheets. This subject-matter does not appear in the Specification as accepted.