| 摘要 |
1487447 Foundry mould compositions DEUTSCHE TEXACO AG 13 Aug 1975 [20 Aug 1974] 33765/75 Heading C3N A composition suitable for the manufacture of foundry moulds and cores using the cold box method comprises sand and a two-component binder system of an acetone-formaldehyde condensation product and a polyisocyanate, the acetone-formaldehyde condensation product being a polymethylol having a molecular weight of 140-220 that is obtained by condensing acetone and aqueous formaldehyde solution in a mole ratio of acetone : formaldehyde of 1À0 : 1À0 -2À5 in the presence of aqueous alkali, the mole ratio of alkali to acetone being in the range 0À011 :1 to 0À15 : 1, until the reaction mixture is substantially neutral, acidifying the substantially neutral mixture with aqueous acid solution to a pH value of 4 or below, and removing water to a solids content of at least 95% by weight. The alkali is preferably sodium hydroxide whilst the aqueous acid used in the neutralization may be any mineral acid or organic acid. The polyisocyanate is preferably 4,4<SP>1</SP>-diphenylmethane diisocyanate. In the specific examples the sand, polyisocyanate and acetone-formaldehyde solution are mixed and then subsequently cured with atomized triethylamine. |
