| 摘要 |
PURPOSE:To obtain the titled resin having low molecular weight and high welding temperature, curable quickly, and giving a cured product having high strength, by carrying out the novolak reaction of phenol with formaldehyde at a low molar ratio, dehydrating and dephenolating the product, and removing the dinucleus component. CONSTITUTION:(A) Phenol is made to react with (B) formaldehyde at a molar ratio (A/B) of 0.3-0.7 in the presence of an acidic catalyst to obtain a precondensate. The product is dehydrated and dephenolated, and the dinucleus component is removed by distilling the mixture in vacuum while introducing steam into the mixture when the reaction temperature reaches 180-200 deg.C, until the content of the dinucleus component and that of the high-molecular components having >=6 nuclei in the whole resin reach <=15wt% and <=55wt%, respectively. USE:Resin-coated sand for the casting mold, etc.
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