The hot box process for the production of foundry cores utilizes a hot box resin, either a liquid phenolic or a liquid furan resin, that is cured through the use of heat and a Hot Box Catalyst. These resins are mixed with sand and an appropriate catalyst, and then blown into a heated pattern to initiate the reaction. The hot box catalysts are referred to as latent acid catalysts. That is, these catalysts are not acidic in nature, but under the effect of heat they will decompose to produce a weak acid. This weak acid then, in conjunction with heat, initiates the curing reaction of the hot box resins, and allows for the production of strong cores using the hot box process.
Hot box catalysts are water solutions of urea and ammonium salts of strong acid. They may also contain other materials, such as release agents or buffering agents, at low levels. A large variety of catalysts are available, varying primarily in the type of salt and the amount of salt present in the catalyst. The type of salt and the amount of salt used will affect the strength and speed of the catalyst.
Because hot box catalysts are a source of weak acid, anything that can neutralize this acid will adversely affect the performance of the hot box resins. Therefore a sand with higher Acid Demand Value, or a higher content of basic material, will require a stronger catalyst under the same process conditions. The particular catalyst to be used in a given situation will depend on:
- The type of sand
- The Acid Demand Value of the sand
- The core box temperature
- The core size and configuration
Health & Safety Information:
Explosion, equipment damage, and/or personnel exposure may occur if hotbox resins and their acid catalysts are mixed together without adequate sand to absorb the heat of the resulting reaction. Ensure your facility has good labeling, safety procedures, and training to prevent inadvertent mixing, specifically focused on preventing unloading errors. Personnel must be trained to immediately evacuate the potentially affected area in the event these resins are inadvertently mixed with acid catalysts or other acidic materials.
Carefully review the MSDS for safety information that may be relevant to your operations. Develop the means to manage product hazards before ordering. Contact our product safety group if you require assistance in understanding or managing these issues.