Preparation method of phenolic resin for precoated sand

The invention discloses a preparation method of phenolic resin for precoated sand. The method comprises the following steps: (1) preparation of an activated carbon catalyst: soaking particle activated carbon in an acid liquor, filtering, drying and cooling; and (2) preparation of phenolic resin for precoated sand: adding phenol into a reaction kettle, adding the activated carbon catalyst, adding formaldehyde, carrying out backflow at 100 DEG C, maintaining backflow for 4-8 hours, distilling and dehydrating, vacuumizing and dehydrating, cooling and adding a silane coupling agent after reaching the softening point, and agitating for 15min to obtain the phenolic resin for precoated sand. According to the preparation method of phenolic resin for precoated sand provided by the invention, the activated carbon immobilize acid is used as the catalyst and the corrosion to the device is small, so that the obtained phenolic resin is good in flowing property, high in strength, low in free phenol and excellent in high temperature resistance. The precoated sand prepared by the phenolic resin is easy to coat, the adding amount of phenolic resin is reduced, and the production cost is lowered.