| 摘要 |
PURPOSE:To provide resin-coated sand for a casting which prevents the crack to be generated particularly in the stage of charging a molten metal into a casting mold by allowing a resin which is obtd. by a reaction of a compsn. composed of bisphenol A and bisphenol F at a prescribed weight ratio and an aldehyde and is solid at an ordinary temp. to exist. CONSTITUTION:A compsn. contg. the bisphenol A expressed by the formula I and the bisphenol F expressed by the formula II at 98/2-80/20 weight ratio and aldehyde are brought into reaction with each other in the presence of a catalyst such as oxalic acid or the like and a resin which is solid at an ordinary temp. is prepd. HCHO, CH3CHO, etc. are used for said aldehyde. The number average mol.wt. of said resin is more particularly preferably 350-750. <=4pts.wt., for example, 4pts.wt. said resin is compounded with 100pts. molding sand and both are kneaded, whereby the intended resin-coated sand for casting is obtd. Such resin-coated sand produces no malodor during charging of a molten metal and obviates the decrease in a collapsing property. |
