Patent GB-530271-A (GB)
Title: Improvements in or relating to the production of thermoplastic materials in fibrous or cellular form
IPC: C08L1/10
Filed: 1939-06-08
Abstract: 530,271. Cellular compositions ; moulding. TAYLOR, W. I. June 8, 1939, No. 16814. [Classes 70 and 87 (ii)] [Also in Group IV] Thermoplastic material in fibrous or cellular form is obtained by subjecting to elevated temperature and pressure a composition comprising the thermoplastic material, e.g. cellulose acetate, and a solvent liquid in such concentration that the composition is not flowable under ordinary temperatures and pressures, until the temperature of the composition is substantially uniform, and then suddenly releasing the pressure to permit rapid vaporization of the solvent and drying of the material into a mass of low specific gravity. The release of pressure may be arranged to permit expansion of the mass into the chamber in which it is confined during application of the high temperature and pressure, the mass thereupon assuming the shape of the chamber. The release may, however, be effected through an aperture in the chamber to permit the mass to be extruded into the atmosphere or into a container or mould. A cellulose acetate-acetone plastic may be used to produce a voluminous continuous thread by extruding the heated mass through a small hole. The mass sets to a continuous thread of individual fibres connected together at intervals. The pith-like masses produced by the process may be resilient or flexible according to the size of the cavities produced. Pressure may be applied by a piston, a screw, or fluid pressure. Non- solvents, e.g. water, or pigments, e.g. kieselguhr, or asbestos, cellulose, or other fibres, or plasticizers may be included in the cellulose derivative composition. The fibrous or cellular compositions obtained may be used for heat or sound insulation, or making life-belts particularly when they contain or are treated with waterrepellent substances, or in aeroplane construction for imparting buoyancy in the event of forced descents on water. The thermoplastic material may be cellulose acetate, propionate, butyrate, acetobutyrate or other ester, or methyl, ethyl, benzyl, or other cellulose ether. Dioxane, methyl ethyl ketone, methyl acetate, benzene, and other appropriate solvents may be used. As shown in Fig. 1, a cylinder 1 fitted with heating jacket 2 has a closure plate 3 pivoted at 4 so that it can be held across the opening of the cylinder by screw 5 or quickly moved aside. A plunger 6 has a phosphorbronze head 7. Pressure is exerted on the mass 8 within the cylinder by means of a ram 9. The cross-section of the cylinder may be of circular or other shape. When the mass in the cylinder has been heated under pressure for such a time that it is uniformly fluid, the ram 9 may be quickly withdrawn to allow the material to expand within the cylinder. Alternatively the closure plate 3 may be slid away to allow the material to be expelled and to form a cellular mass. As shown in Fig. 2, the material 11 is expelled by continuous pressure on plunger 14 through the outlet 15 upon release of cock 16. Below cock 16 is a jet 17, orifice 18, and mould 19. If the cylindrical mould is provided with a central rod, a hollow tubular product may be obtained. As shown in Fig. 10 a short shaping tube 24 is provided. The extruded cellular rod is directed to pairs of corrugated feed rolls 25. As shown in Fig. 11 a mould 27 with heating jacket 28 is provided with a plunger 29 connected by links 30 to a lever 31 and ram 32. The plunger is allowed to rise quickly by movement of links 30 and the thermoplastic material is formed into a block having the shape of the mould 27. As shown in Fig. 12 pressure is applied to the material 37 by the plunger 35 and ram 34. The plunger 35 is then locked by pins 38 while the material 37 is brought to a uniform temperature e.g. in a stove. The pins 38 are then withdrawn permitting rapid expansion of material 37. As shown in Fig. 14, a cellulose acetate-acetone plastic is rendered fluid by heat and pressure in cylinder 46 and is discharged through jet 48 into the atmosphere. A thread consisting of fine fibres is obtained.