| 摘要 |
Urea-formaldehyde castings are obtained by adding to a preformed urea-formaldehyde condensate an aqueous solution containing an acid setting agent, an albumen, and free urea, casting the mixture in a mould of the desired pattern until it sets sufficiently to be removed therefrom and allowing or assisting the cast product to harden. Albumens specified are glues, blood or egg albumen, gelatine; sulphuric, lactic, citric, tartaric, oxalic, hydrochloric, salicylic, acetic acids and aluminium chloride or sulphate may be used to set the resin. 30 c.cs. of a 60 per cent urea-formaldehyde condensate are mixed in a mould with 5 c.cs. melted glue (50 per cent water), 8 gs. urea, 3 c.cs. 25 per cent phosphoric acid, and 2-3 gs. aluminium chloride. The cast product may be hardened at 40-80 DEG C. in a bath containing alum solution.
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