| 摘要 |
<p>1,210,240. Coated sand. BORDEN CHEMICAL CO. (U.K.) Ltd., and FESLENTE Ltd. 8 Oct., 1968 [14 Nov., 1967], No. 51867/67. Heading C1A. [Also in Division C3] A substantially, nitrogen-free moulding composition is produced by mixing a granular refractory material with a solution or suspension of a novolak resin and a liquid resole so as to coat the granules, adding a minor amount of a waxy material, evaporating out volatile material whilst continuing mixing until the mixture is free-flowing and reducing the pH, if necessary to below 5À5. The novolak may be prepared from phenol and formaldehyde (as formalin) in a molar ratio between 1: 0À5 and 1 : 0À9 with sulphuric or hydrochloric acid as catalyst. It may be dissolved in IMS or a mixture of water and IMS. The resole may be prepared from phenol and formaldehyde (as formalin) in a molar ratio between 1 : 1À2 and 1 : 3À5 with magnesium oxide or sodium hydroxide as catalyst. The novolak and resole may be mixed before addition to the refractory material which may be sand. The waxy material may be calcium stearate or a polyamide in which some of the free amino groups have been condensed with stearic acid. 1-10% may be used. The pH may be adjusted wtih salicylic acid. The mixture may be used to make foundry moulds.</p> |
