Foundry resins are the binders used with foundry sand to make moulds and mould cores. MDI is used in the ‘cold process, which produces accurate sand castings without heating, saving energy, time & capital compared to the urea-formaldehyde & phenol-formaldehyde resins. In the ‘cold process’, a phenolic resin and Polymeric MDI are mixed with sand. The mixture is poured into a mould in an enclosed box. A rapid-curing reaction is then initiated by the introduction of a volatile amine catalyst carried in a stream of air or carbon dioxide. The ratio of binder to sand is 1-2% by weight.