GB493078A - Improvements in or relating to composite building boards - Google Patents

Abstract

Composite building boards are produced by allowing core material to set in contact with a liner or liners which are coated or impregnated with uncured thermohardening resin which is dried without converting the resin to its final condition, and then subjecting the board to heat treatment to harden the resin. Either urea-, thiourea-, or phenol-formaldehyde resins may be used and they may penetrate the liner partially or completely. In an example a white board was impregnated with a 60 per cent solution of a 50 per cent resin syrup containing 1 1/2 molecular proportions of formaldehyde to 1 of urea and catalysed with 0,1 per cent sulphuric acid. In a second example the core comprised in addition 15 parts of resin syrup similar to that used for impregnating the liners. The resin syrups described in Specification 491,882 may also be used and acid catalysts are added to accelerate the resin condensation.ALSO:Composite building-boards are produced by allowing core material to set in contact with a liner or liners which are coated or impregnated with uncured thermo-hardening resin which is dried without converting the resin to its final condition, and then subjecting the board to heat treatment to harden the resin. The core material may comprise plaster, cement, &c., and the liners may be of paper, pulpboard, &c. The board may be formed in known manner by passing the liners, with the core material between them, between rollers. Either urea-, thiourea-, or phenol-formaldehyde resins may be used and they may penetrate the liner partially or completely. In the latter case and additional paper liner may be used next to the core. The liner may be decorated by plain or printed colours or by embossing. In an example, a white board was impregnated with a 60 per cent solution of a 50 per cent resin syrup, containing 1 1/2 molecular proportions of formaldehyde to 1 of urea and catalysed with 0,1 per cent sulphuric acid. The board was dried at a low temperature leaving the resin uncured and applied on both side of a core consisting of 100 parts by weight of Plaster of Paris, 10 parts of sawdust, and 55 parts water. The formed board was passed through a drier whose inlet was at a temperature of 150 DEG C. and outlet at 65 DEG C., and the board was then ironed at 140 DEG C. and polished. In a second example the core comprised in addition 15 parts of resin syrup similar to that used for impregnating the liners. The resin syrups described in Specification 491,882, [Group IV], may also be used in the present invention and acid catalysts are added to accelerate the resin condensation. The final board may be baked for 6 hours at 60 DEG C. to improve its water-resistance.