Patent GB-600961-A (GB)
Title: Improvements in or relating to the impregnation of wood with urea-formaldehyde resins
IPC: B27K3/15
Filed: 1945-09-19
Abstract: 600,961. Impregnating wood; proofing permeable materials. DU PONT DE NEMOURS & CO., E. I. Sept. 19, 1945, No. 24194. Convention date, Sept. 20, 1944. [Class 140] Wooden objects, including veneers and plywood, are impregnated with a neutral to slightly alkaline solution of a methylol urea in water or an aqueous organic solvent while maintaining the methylol urea substantially entirely in a monomeric state, drying, and then heating the surface of the dried, impregnated wood to 240-350‹F. for ¢-5 minutes at a pressure in excess of the crushing pressure of the wood at that temperature. The product has a compressed, hardened surface that can be readily polished and is resistant to weak acids, and the weather. The ratio of formaldehyde to urea may be between 1.1 to 1 and 1.75 to 1. A minor proportion of melamine may be included, and the solution may contain a polymerisation accelerator, or a dye. The drying may be by air-drying, kilndrying, or a combination of both methods. Aqueous solvents specified are aqueous methanol, ethanol, propanol, glycols, glycol ethers, dioxolane and dioxane. Buffers such as di- or tri-ethanolamine, sodium polymethacrylate, hexamethylene tetramine, monomethanolamine, sodium acetate, borax, and mono-sodium phosphate may be added. Minor proportions of other modifying materials may be added, such as phenol, dicyandiamide, cyanamide, guanidine, thiourea, methylol phenol, methylol melamine, alkyl ethers of dimethylol urea, hexamethylene tetramine, ammonium thiocyanate, dextrose, beta, beta-dihydroxy diethyl formal, dioxolane, glycols, glycerol formals, polydioxolane, dimethylol diglycolamide, bismethoxymethyl adipamide, methylol hydroxy acetamide, methylene diformamide, N-ethylol formamide, hydroxyacetamide, diethanolamine, diethylaminoethyl methacrylate, 5, 5 - dialkyl hydantoins, alkyl ureas, methoxymethoxyethyl urethane, methylol guanidine, thioammeline, 1, 3, 5-alkoxyalkoxy-aminotriazines, ammeline, and ammelide. Fire retardants such as boric acid, borax, and sodium phosphate, and materials to prevent attack by organisms, including sodium chlorophenolates, copper or mercury naphthenate, salts of monochlorophenyl phenols, di-, tri-, tetra-, and pentachlorophenols, 2-chloro-6-cyclohexylphenol, tetrachlorocresol, 4-chloro-5- xylenol, dinitrophenol, fluorides, chromates, and arsenates. Moisture repelling agents and porefillers such as long chain amidomethyl-pyridinium chloride, wax, glycerine, polyolefines, polyethylene ethers, polyvinyl resins, insoluble soaps, anthracene, rosin, rosin ester, alkyd resin, chlorinated naphthalene, and titanium oxide may also be added to the solution. The wood may be in the form of lumber or of shaped objects such as telephone poles, railway ties, barrel staves, window sashes, shuttle blocks, drawtwister tubes, and bobbins. Green wood may first be treated with urea solution. The wood may be impregnated at ordinary or slightly raised temperature by long soaking, or with the aid of vacuum and pressure which may alternate several times. The pressure surfaces may be of stainless steel coated with a zinc soap. Specifications 549,335 and 584,380 are referred to.