Sand coating resins have low phenol content, developed to coat silica sand in the production of "Shell Molding" or "Croning" process. This type of resins can be in the form of flakes or drops, as well as in the form of liquid as novolac resins.
The shell casting process is generally preferred in the production of grift and high surface quality casting parts. Thanks to the mold with high strength in the shell casting method, grift parts can be cast perfectly. Resin-coated sand forms the basis of the shell casting method. Resin is added to sand, through sand performance additives, they completely cover the surface of the sand with proper bonding area.
Ideal Usage Recipe
Hot coating method : Washed and dried silica sand is heated to 120-150 ºC and phenolic novolac resin is added at the weight 1-5 % to sand. The molten resin is wrapped in sand grains and the sand is covered. Afterward, HMTA is added as an aqueous solution of 15-20 % compared to the resin for final curing. In addition, calcium stearate is added to increase fluidity.
Warm coating method : The resin is used as a solution in methanol and water. Firstly, powdered HMTA is added to the sand and the sand is heated to 60-90 ºC. Then the resin dissolved in alcohol is added to the sand and the sand is coated. At this time, hot air is blown into the mixer, allowing the alcohol and water to evaporate. The sand coating is finally completed with the addition of calcium stearate.
Product Advantages
- Eco-friendly formulation
- Low free phenol / formaldehyde content
- Low emission value
- Less odor release during coating and casting
- Providing excellent sand fluidity
- Performance features with high peel back resistance
