GB1386347A - Process and apparatus for the production of sheets of phenolic resin foam - Google Patents

Abstract

1386347 Moulding foamed sheets; laminates DYNAMIT NOBEL AG 1 March 1972 [2 March 1971 2 Dec 1971] 9636/72 Headings B5A and B5N [Also in Divisions C3 and B1] Phenolic resin foamed sheet is continuously produced by forming a premix of a liquid phenolic foamable resin and a blowing agent; mixing the premix with hardener, uniformly distributing the mixture on to a lower cover layer entering a double-belt press and covering with an upper cover layer as it enters the press and heating as it passes through the press to foam and harden. The cover layers may either be stripped off or left on and accordingly they may be coated or impregnated with adhesive or release agent. The sheet produced may be trimmed, cut into lengths and grooved longitudinally and transversely. The density of the sheets produced increases outwardly from the middle. The apparatus comprises storage vessels and metering pumps 6-9 for the various ingredients, the liquid resin being cooled, 11, and passed to a two-stage premixer 12, also cooled, and thence to a mixer 13 which also receives the hardener and additives. This mixer is divided into upper and lower communicating chambers by either a disc on the mixer shaft (Fig. 4, not shown) or an encircling web on the inner wall of the mixing vessel (Fig. 5, not shown), or both forming a labyrinth seal (Fig. 6, not shown). Hardener is supplied to the lower chamber only, so that hardener resin will not come into contact with the bushing by which the shaft is journalled through the vessel housing. The area of the communicating gap between the two compartments is smaller than that of the resin inlet to the upper compartment so that this compartment is pressurized. A nozzle 23 distributes the mixture on to the lower cover layer 42, this having been folded at the edges through 90 degrees to form upstanding sides. The resin is levelled by roller 22 and the upper cover layer applied, the upstanding edges of the lower cover layer then being folded inward over the upper cover layer, by device 24, to form a seal as the layers pass between the lower belt 27 and upper belt 26, the latter being vertically adjustable by hydraulic rams 28. Rubber beading 25 rotates with the belts and is engaged by rails on the belts to form side wall seals. Heating is by a combination of internally placed heating elements and a forced-draught hot air system (Fig. 3, not shown). The cover layers may be taken off by rolls 29 and 30 as the panel emerges through the belts to pass through cutting and grooving devices 32 to 37 to be stacked 38.