JPS5116484B1 - - Google Patents

Abstract

1338080 Fire-proofing wood KANAMARK DANISH CANADIAN ENG CO Ltd AS 21 Dec 1970 [23 Dec 1969] 60579/70 Heading D1P A method for the fire-inhibiting impregnation of wood, e.g. in the form of veneers, sheets, flakes, chips or sawdust, comprises impregnating the wood in a dry state with a solution of a monomer component selected from phenol, dihydroxybenzenes, urea, melamine and mixtures thereof, heat treating to remove the solvent, impregnating with a formaldehyde solution, and heat treating to remove the solvent and to form a polymeric material by reaction of the monomer component with the formaldehyde. A fire inhibiting salt such as borax, and boric acid, may be incorporated in the monomer component. The solutions may be aqueous and applied at normal or reduced pressure, and at elevated temperature. In a plant for continuously carrying out the above method, wood is cut at 1 into a strip of veneer which is wound on a roll 2. Veneer from the roll is passed through a section 3 of a 160‹C oven for drying, through a double curtain of liquid for impregnating with the monomer component, through a second oven section 6 for solvent removal, through a double curtain of liquid at 7 for impregnating with the formaldehyde, through a third oven section 9 for solvent removal and polymer formation, and through a cooler 10 before being cut at 11 into lengths 13. In a modification, Fig. 2 (not shown) the oven sections 3, 6, 9 are replaced by separate longitudinally spaced ovens and the impregnation is effected by immersion. In a further modification, Fig. 3 (not shown) for carrying out the method discontinuously, the veneer is passed repeatedly through a single oven. For the impregnation of wood chips &c., the Figs. 1, 2 and 3 apparatus may incorporate a perforated conveyor belt for the transport of the chips &c. For the treatment of sawdust, a non-absorbing glass or nylon fibre conveyor belt is used.