| 摘要 |
Foamed synthetic resins based on mono-, dior trimethylol ketones or mixtures thereof or on precondensates obtained by subjecting these compounds to a mild thermal treatment are prepared by a process in which, before foaming and condensing of the methylol ketones or their precondensates with solutions of alkali metal hydroxides, there is added a very finely-divided metal powder or flake which is capable of reacting with the alkali metal hydroxide with the evolution of gas. The preferred metals are aluminium, magnesium and zinc or alloys thereof, e.g. aluminium bronze powder. The metal powder or flake is preferably used in an amount of about 0.5% by weight of the reaction mixture as a whole. Fillers or stiffening or strenthening materials may be added before or during foaming. |
