Patent GB-931531-A (GB)
Title: Board products and processes for their manufacture
Inventor: CHAPMAN RALPH
IPC: D21J1/00
Filed: 1959-09-29
Abstract: 931,531. Laminates and laminating; making paper; paper. R. G. WHEELER, R. CHAPMAN, R. A. MIX, T. L. GRIFFIN, E. A. BUCKTHORN, and O. E. CHEATHAM, [trading as WOOD PROCESSES, OREGON Ltd.]. Sept. 29, 1959, No. 33086/59. Classes 96 and 140. Laminated boards comprise a core of coarse wood elements such as plane shavings, veneer flakes or sawdust, bonded with a preferably powdered thermosetting adhesive, and surface layers of paper pulp applied as felted mats formed under vacuum from a thin aqueous slurry of cellulose fibres, the outer faces of the surface layers being coated with a drying oil, the assembled layers being consolidated under heat and pressure. As shown, veneer flakes 10 are delivered by a conveyer 14 to an inclined tumbling drum 13 having longitudinal ribs 19, and are coated with powdered adhesive 15 delivered from a hopper by a dispensing conveyer 16. The adhesive may be soya bean flour, or a water-insoluble solvent-soluble phenolic resin, or mixtures of these in various proportions, and may contain fungicides, insecticides, germicides or other active materials. The adhesive is such as to adhere only to the surface of the core material. A sizing material such as paraffin emulsion may be sprayed on to the adhesive-coated flakes through a pipe 18. The treated flakes are delivered to, and conveyed to a bin 22, Fig. 5, on a conveyer belt 21 from which they are swept by an oscillating brush 27 extending right across the bin. An aqueous slurry of cellulose fibres is delivered to a tank 40 by a pipe 41 controlled by valve 42 and is converted into a wet felted web 31 by a suction drum 43 having radiant heaters 45 above it to effect partial drying of the web. The slurry may be made from reclaimed magazine paper, the filler in which is advantageous in making the paper surface layers less porous, and may be deinked or dyed. Linseed or tung oil or a synthetic drying oil or petroleum origin is applied to the web 31 by a roller 46 dipping in a trough 47, and the oil is partially dried by infra-red lamps 81. The web is led by a roller 8 beneath the bin 22 supported on caul plates 30 on a conveyer, and is showered with adhesive-coated core material to form a uniform layer. A second web 32, formed and treated similarly to web 31, is delivered above the core material and the sandwich so produced cut into boards between the caul plates by a rotating knife 33. The caul plates 30 with the unpressed boards are placed on platens 50, Fig. 6, each of which comprises top and bottom plates 51, 52, separated by vertically disposed spaced plates 53 between which heated air, as from apparatus 60, 61, may be passed. The lower plates 52 carry spacing members which limit the final degree of compression of the boards. The loaded platens are placed in succession at the bottom of the pile and are heated for about one-third of their travel to the top of the pile, being allowed to cool thereafter. Wire screens 56 may be used to impress a pattern on the boards; otherwise they are produced with smooth surfaces. The pressed boards may be finally cooled by stacking in vertical position separated by spacer laths, the stacks being held together by clamps.