| 摘要 |
584,380. Treating wood. IMPERIAL CHEMICAL INDUSTRIES, Ltd. (Du Pont De Nemours & Co., E. I.). May 17, 1944, No. 9436. [Class 140] Wood is hardened by treating at least the exterior portions with a solution prepared by dissolving a methylol urea compound in water, and drying. Solutions formed by dissolving urea and dimethylol urea or equimolecular proportions of monomethylol and dimethylol urea in water are suitable. The pH of the solution is maintained between five and nine by the addition of acetic or sulphuric acids, or of ammonia or caustic soda. The wood is dried and is then impregnated either by soaking in the solution for eight to eighteen days or is impregnated by a vacuum pressure cycle. The latter comprises subjecting the wood to a vacuum of not more than 100 mm. of mercury, immersing the wood in the solution while still under vacuum, releasing the vacuum and allowing the solution to be absorbed at atmospheric pressure or under a pressure of several atmospheres perhaps in an atmosphere of nitrogen, and then drying with, if desired, the application of heat to promote condensation of the compound. During or after the final heating the article may be subjected to a pressure of from 0.5 to 1.5 tons per square inch to produce increased hardness. Articles are preferably roughly machined before impregnation, the final machining being completed after treatment. Specification 549,335, U.S.A. Specification 1,991,056 and French Specification 748,854 are referred to.
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