Patent GB-1318076-A (GB)
Title: Processes for treating articles of porous material
IPC: B27K3/15
Filed: 1970-08-14
Abstract: 1318076 Coating porous substrates CONSERVATOME 14 Aug 1970 [14 Aug 1969] 39318/70 Heading B2E [Also in Division C1] An article of porous material is treated by impregnating the article with polymerisable liquid, coating the impregnated article with a protective substance capable of producing a product under irradiation which is oxidisable by oxygen and polymerising the polymerisable liquid by irradiation. The protective substance can be a wax of mineral, vegetable or animal origin e.g. paraffin or microcrystalline waxes, waxes formed of esters of higher fatty acids or alcohol, carnauba and bees wax; fatty acids solid at ambient temperature e.g. a mixture of stearic and palmitic acid. These substances may be applied as melt, emulsion or solution. The protective substance may also be a solution in a monomeric liquid e.g. methyl methacrylate of a polymer obtained by hardening the monomeric liquid, the monomer being evaporated after impregnation; a strippable varnish e.g. a copolymer vinylchloride and vinylacetate, the coating of varnish being subsequently removed after irradiation; a solution of unsaturated polyesters in a polymerisable solvent. The porous material may be wood, plaster. The polymerisable liquid for impregnating the articles may comprise a solvent which is also polymerisable e.g. mono- or divinyl benzene and polyester, acrylic or urethane resins. As shown in (Fig. 2) blocks (1) of beech are separated by plates (2) of paraf-. fined cardboard or a polyethylene grill and are arranged in open work baskets (3) of aluminium or aluminium alloy. The assembly is then introduced into a container which is put under low pressure to degas the beech and the vessel then filled with polymerisable liquid. The vessel is then pressurized for 18 hours to impregnate the beech wood to its core. The baskets are then removed, drained and then inserted in aluminium containers into which is poured a bath of molten paraffin wax. The wax is then solidified into a block surrounding the wooden blocks and the container then subjected to an irradiation dose. The irradiation heats the wax block to the liquid state and polymerises the liquid which impregnates the beech. After irradiation the baskets are removed from the containers, cut into elements for making flooring blocks, and rubbed down or planed. The polymerisable impregnation liquid may comprise 20 parts styrene, 10 parts methyl methacrylate, 10 parts acrylonitrile and 60 parts of an organic resin prepared from 1, 3 propylene glycol, maleic anhydride and phthalic anhydride. In example 7 cylindrical elements of graphite are impregnated with a polyester resulting from the reaction of fumaric anhydride with bis-phenol in solution in styrene and soaked in a bath of liquid strippable varnish constituted by a copolymer of vinylchloride and vinylacetate dissolved in acetone. After drying the coated elements are subjected to irradiation and the coating of varnish subsequently removed. The elements are then transformed completely into graphite by baking at 800 to 1000‹C followed by heating to 2300‹C.