| 摘要 |
Finely-divided acetals are obtained by adding a finely-dispersed aromatic aldehyde of the benzene or naphthalene series to an aqueous solution of polyvinyl alcohol containing not more than 10 per cent by weight of the total and reacting at a temperature less than 80 DEG C. in the presence of an acid catalyst present in low concentration. Specified aldehydes are benzaldehydes, chlor - benzaldehydes, nitro - benzaldehydes, tolualdehydes and naphthalde hydes. Acid catalysts given are hydrochloric, sulphuric, oxalic and chloracetic acids, ammonium, zinc or aluminium chlorides. The acetals may be dyed either during or after preparation with either basic dyestuffs or those containing basic groups. Emulsifiers such as sodium dioctyl disulpho succinate, sodium 1 - isopropyl - 2 - naphthalene sulphonate, the sodium salt of oleyl sulphate and the hydrochloride of diethylamino-ethyloleylamide, may be present. Titanium oxide, polymethyl methacrylate, monomethylol urea and benzoic acid, triacetin and benzyl alcohol may be added to the acetals. Pigments and moulding powders are specified uses. |
