GB743401A - Method for the production of articles by moulding substances of vegetable origin under pressure and at elevated temperatures - Google Patents

Abstract

743,401. Moulding articles from woodwaste etc.; plastic compositions. RUNKEL, R., and JOST, J. Aug. 15, 1950 [Oct. 1, 1948; Sept. 7, 1949], No. 20276/50. Classes 70 and 87 (2). Moulded articles are produced by pressing, in a first stage, substances of vegetable origin which contain resin-forming groups and carbonyl groups at temperatures between 125 and 280‹ C. and pressures between 50 and 300 atms. to produce water vapour and volatile reaction products, and, in a second stage, reacting the material in the mould with the volatile reaction products of the first stage. The materials used include wood, e.g. veneers or sawdust, seeds, seed husks, stalks, and lignin from brown coal. The raw material may be first decomposed by biological means, e.g. by using fermenting agents. Weak acids, such as the lower aliphatic acids, may be added, or, if the material is too strongly acid producing, bases such as ammonium hydroxide may be added. Phenols, aldehydes, various plasticizers or hardeners may be added. Fillers such as clay, powdered glass, zinc oxide, mica, heather or lignin may be incorporated in the material to be moulded. Metal parts, such as hinges, fish-plates, dowels, plates, eye-pieces, wires, &c. may be incorporated in the articles during the moulding process. The whole process is carried out in a gas-tight mould which may be sealed by means of the raw material. Gases which do not take part in the reaction, such as carbon monoxide and carbon dioxide may be removed from the mould during the first stage of the reaction. Alternatively, gases capable of taking part in the reaction or their conversion products removed from the mould in the first stage of the same or a previous reaction may be supplied to the mould in the second stage. Preferably the water content of the starting material is adjusted to between 10 and 17 per cent. Heating of the material in the mould can be interrupted after the beginning of a constant pressure period when no more gases are evolved. Thereafter, the material is cooled. External pressure may be applied. The heating and pressure may be adjusted to maintain constant temperature and pressure at the desired values throughout the operation. The reaction may be interrupted after the first stage, the intermediate reaction product being powdered and then fully condensed in the final stage which may be an injection, casting, extrusion or compression operation. A compression mould suitable for the process comprises a heated plunger 17. Layers of shavings 8, 10, 12 are separated by metal plates 9, 11. The mould is sealed by means of compressed sheets 4, 6, 14, 16 obtained from a previous moulding operation. These sealing plates alternate with metal plates 5, 7, 13, 15.