Patent ID: 7855240

Claim:
A polyurethane foam for insulating structures that is produced from a polyurethane spraying system, said polyurethane foam being the reaction product of: a) a resin component comprising; a blowing agent present in an amount of from 15 to 40 parts by weight based on 100 parts by weight of said resin component, a first polyol used in an amount of from 5 to 25 parts by weight based on 100 parts by weight of said resin component and having a number-average molecular weight of from 150 to 500 and having a hydroxyl number of from 250 to 1000 and having at least tetra-functionality, a second polyol having a number-average molecular weight of from 3500 to 8000 and having a hydroxyl number of from 20 to 100 and having terminal hydroxyl groups, and a curing component used in an amount of from 2 to 15 parts by weight based on 100 parts by weight of said resin component and comprising a polyether amine having at least one primary amine group, an equivalent hydroxyl number of from 20 to 800, and having a number-average molecular weight of from 150 to 5000, and b) an isocyanate component comprising diphenylmethane diisocyanate; wherein said a) and b) are reacted in a volumetric ratio having an isocyanate index of from 25 to 60; and wherein said polyurethane foam is open-celled and has a density of less than 1 pound per cubic foot and low water absorption as a result of reacting said a) and b) in said volumetric ratio at said isocyanate index.