Patent GB-847611-A (GB)
Title: Laminated boards or panels
Inventor: DAVIS ERNEST ALEC
IPC: B27D1/04
Filed: 1956-11-27
Abstract: 847,611. Laminates; treating wood. FORMICA INTERNATIONAL Ltd., [formerly FORMICA Ltd.]. Nov. 21, 1957 [Nov. 27, 1956], No. 36247/56. Class 140. [Also in Group XXIII] Laminates.-A laminated board or panel comprises a combination of a lamina or laminae of wood of the species Ceiba Pentandra or wood of the genus Bombax and laminµ ofother fibrous material bonded together under heat. and pressure by thermosetting synthetic resins, with the laminµ of other fibrous material disposed on both external faces of the wood lamina or laminµ, the internal cells of the wood lamina or laminae being substantially free of synthetic resin and the lamina or laminµ of wood being compressed from its natural state not more than 5%. The board or panel may comprise wood laminµ interleaved with resin-impregnated sheets of paper or other fibrous material. The fibrous material laminae may comprise two or more sheets of resin-impregnated paper of which the surface sheet is transparent or translucent and the sheet next thereto is formed with a decorative pattern. The laminate may be made (a) by coating a lamina of one of the specified woods on each surface with a thermosetting synthetic resin, applying to said coated surfaces one or more fibrous sheets each impregnated with a thermosetting synthetic resin, and bonding together under heat and pressure, said heat being sufficient to cure the synthetic resin and the pressure not exceeding 200 lb/in.<SP>2</SP>; or (b) by assembling a stack of laminµ of one of the specified woods, each coated with a thermosetting resin, applying to said stack on both surfaces one or more fibrous sheets impregnated with a thermosetting synthetic resin and bonding under heat and pressure as above; or (c) by forming a plywood core consisting of laminae of one of the specified woods and pressed under a pressure not exceeding 200 lb/in.<SP>2</SP>, applying to both faces of the plywood core thermosetting resin-impregnated paper or other fibrous sheets and bonding under heat and pressure as above; or (d) by forming the resinimpregnated fibrous sheets as a decorative laminated sheet and bonding under heat and pressure as above to a plywood core formed as in method (c); or (e) by applying a separately formed decorative laminated sheet of resinimpregnated paper or other fibrous sheets consolidated under heat and pressure to both external faces of an assembly of laminµ of one of the specified woods and subjecting the stack to heat and pressure as above. In an example, veneers of Ceiba Pentandra are coated with phenol-formaldehyde resin, and stacked to gether. On either side of this stack are placed sheets of paper impregnated with a phenolformaldehyde resin, and, on the external faces of these, decorative paper sheets impregnated with urea-formaldehyde or melamine-formaldehyde resin and this sheet is surfaced by an alpha-cellulose sheet impregnated with a melamine-formaldehyde resin. The resins are cured -and the stack consolidated by heat and pressure. According to the Provisional Specification, the wood may be Bombax Buonopozense or Mugongo of which Ricinodendron Rautanenii is stated to be a species; melamine-formaldehyde resins used to impregnate alpha-cellulose sheets may have added to them 0.1-10% by weight of finely divided silica; the top layer of paper sheets must be sufficiently thick to prevent the - grain of the top wood veneer from being transmitted to the decorative surface on the application of pressure; and the paper sheets must contain sufficient resin to ensure the production of " homogeneous " articles. Treating wood.-According to the example in the Provisional Specification, veneers from a trunk of Ceiba wood are immersed in a tank containing an aqueous solution of formaldehyde for four hours, dried in a hot air oven, and then laminated as above.