| 摘要 |
<p>An oxymethylene polymer surface is treated with an oxidizing acid to improve the adhesion of a subsequently applied coating. A treatment time of less than 10 seconds is usually used. The polymer may contain oxyalkylene groups, e.g. oxyethylene, up to 20% of the chain. Specified acids are chromic nitric and sulphuric acids, their mixtures and mixtures with non-oxidizing acids, e.g. hydrochloric acid and glacial acetic acid. The acid may be applied by dipping, spraying or brushing. The treated surface may be given a further treatment to produce cross-linked molecules thereon by reacting with formaldehyde from the polymer, e.g. by treatment with a phenol solution containing potassium hydroxide as catalyst and heating to form a surface coating of phenolformaldehyde resin. The phenol may be replaced by urea, melamine, casein, aniline, cresols or xylenols.ALSO:Oxymethylene polymer surfaces which have been treated with an oxidizing acid to improve the adhesion of a subsequently applied coating and which may have been further treated with a compound which forms a resin with formaldehyde (see Division C3) are coated with an ink lacquer or metal. It is preferred to apply a priming coat of clear lacquer before this coating and a clear lacquer. In examples, plaques of oxymethylene-oxyethylene copolymer surface treated as above, are coated with a clear methyl methacrylate lacquer, baked, coated with aluminium by vacuum metallizing, and then coated with a top coat of the clear polymethyl methacrylate lacquer.</p> |
