Preparation of urethane and isocyanurate foams in the presence of a low boiling point blowing agents.

The present invention relates to a process for preparing a rigid, closed cell, polyisocyanate-based foam, comprising contacting and reacting an organic polyisocyanate with an active hydrogen-containing compound, in the presence of water and a blowing agent , characterized in that the blowing agent comprises one or more halocarbon compounds that have a boiling point of 222 to 272 degrees K and is substantially free of an organic compound that has a boiling point of 273 degrees K or higher. An isocyanate reactive composition, comprising a) at least one compound comprising a) at least one active hydrogen-containing compound, having an equivalent weight of 50 to 700 and b) of 1 to 25 weight percent based on the total weight of components (a) and (b) present, of a blowing agent, characterized in that the blowing agent comprises one or more halogen carbon compounds having a boiling point of 222 to 272 degrees K and is substantially free of an organic compound having a boiling point of 273 degrees K or higher, A rigid cell foam closed, polyisocyanate-based, prepared by contacting and reacting an organic polyisocyanate with an active hydrogen-containing compound in the presence of water and a blowing agent, characterized in that the resulting foam contains within its cells a gaseous mixture comprising; a) 10 to 75 mole percent, based on the total moles of (a) and (b) of one or more organic compounds that have a boiling point of 22 to 273 degrees K and (b) of 25 at 90 mole percent based on total moles (a) and (b) of carbon dioxide and which is substantially free of an organic compound that is substantially free of an organic compound having a boiling point of 273 degrees ko superior.