Flexible intumescent fireproofing coating composition

PROBLEM TO BE SOLVED: To produce a curable intumescent composition which, in an unburnt state, can adhere to a substrate without cracking even upon exposure to an extreme change in temperature and weather conditions and can intumesce so as to form a uniform carbonaceous char upon exposure to heat or flame and to thereby protect the underlying substrate from a damage which would be occasioned by a fire. SOLUTION: The intumescent curable composition contains a flexible polyepoxide resin as the resin binder, and the polyepoxide can be cured with a suitable curing agent adapted for this special resin. This composition contains a mixture of (i) zinc, (ii) boron, (iii) phosphorus, and (iv) a material which provides a source of a gas which expands upon heat decomposition. The composition is capable of forming a carbonaceous char upon exposure to heat or flame, with the proviso that the cured, unburnt composition has sufficient flexibility that it passes at least 10 continuous cycles of a cold cycle test without cracking. COPYRIGHT: (C)1996,JPO