Description
Molds are made of green sand, a mixture of silica sand, bentonite, cereal or wood flours, and water or oil. Olivine sand is replacing silica sand to reduce the hazard of silicosis. Bentonite is clay-type mineral that is considered a nuisance dust. Shell molding uses a resin-bonded sand for production of small parts with potential exposure to phenol, formaldehyde, ammonia, hexamethylene tetramine, and carbon monoxide. The core defines the cavity within a casting. The core must be mechanically strong, but friable for easy removal. Modern coremaking uses a series of binder systems. The No-Bake system results in exposures to formaldehyde, phenol, triethylamine, and SO2. MDI may be used, but inhalation exposure is thought to be low during pouring, cooling, and shakeout. Resins may cause allergic contact dermatitis. Chemical hazards associated with using the Hot-Box system include formaldehyde, phenol, silica, furfural alcohol, ammonia, and carbon monoxide. [Burgess, p. 109-26] "Organic binder materials for cores and moulds include furan, phenol-formaldehyde and urethane resins as well as oleo-resinous oils. . . ."Furan binders contain free furfuryl alcohol, which can volatize during mixing, moulding or core-making. Similarly, furan and phenolic resins may emit formaldehyde, phenol and other derivatives by volatilization or thermal decomposition. [IARC 2012: Iron and steel founding] See "Respiratory symptoms and lung function in foundry workers using the hot box method: a 4-year follow-up." [PMID 22173285]