GB1388758A - Manufacture of continuous products consisting of particles and a binding agent - Google Patents

Abstract

1388758 Transversely compressing extrusion die SWISS ALUMINIUM Ltd 1 June 1972 [24 June 1971] 25748/72 Heading B5A A composition comprising binder and small particles, e.g. fibres, or quartz sand, fireclay or aluminium oxide for fire resistant bricks, or carbon or graphite for electrodes for electrolysis of aluminium oxide in a fused fluoride bath, is intermittently extruded as a continuous length through the polyhedral section passage of a mould 10, which is defined by walls which repeatedly slide in contact against each other to move synchronously outwardly and inwardly perpendicular to the direction of extrusion, to effect compression of the composition perpendicularly to the direction of extrusion. The mould 10 comprises a parallel wall outlet, and a tapering wall inlet end into which the composition is delivered by a compacting worm, under a continuous pressure 15 which serves both to prevent reverse flow of the composition when the mould walls move inwardly in the tapering inlet end, and to effect displacement of the mould walls in their outward movement during extrusion of the composition. The die passage may be defined by six, or by four walls as in Fig. 8, which are respectively tapered and parallel at 13 and 14 and which are mounted to effect their inward and outward movement for displacement in guides 22 of a frame 21, in the directions 17 and the reverse directions. Figs. 5 and 6, show the mould walls respectively in their outer and inner positions, with the successive increased hatchings of the extrudate each indicating the extent of extrusion intermediate each perpendicular compression, and the hatchings at 19 and 20 indicating incompletely prependicularly compressed material from the commencement of extrusion, when the die outlet is closed by a plate on the first perpendicular compression. The movement of the mould walls may be effected as a vibratory movement with small displacement, e.g. 0À5 mm., at high frequency, e.g. 10 Hz, producing a carbonaceous extrusion of 1À6 tons per cu. m. A stated composition for anodes for aluminium fusion electrolysis comprises petroleum coke of various grain sizes in stated percentages, with 17% coal tar medium, hard pitch binding agent, the composition being introduced into the extrusion die at 125‹ to 175‹ C., with the die maintained at that temperature. Pitch coke may be used for cathodes of aluminium electrolysis cells. Petroleum pitch may alternatively comprise the bonding agent. The carbon should be amorphous with minimum impurities (10% anthracite, or 0À5% in pitch or petroleum coke).