US Patent 7838568 Insulation boards and methods for their manufacture

A method of manufacturing a polyisocyanurate foam insulation board, the method comprising contacting a stream of reactants that comprise an isocyanate-reactive compound with a stream of reactants that include an isocyanate compound to form a reaction product, where the step of contacting takes place in the presence of a blowing agent and a low-boiling inert gas, and where the amount of low-boiling inert gas present at the time of the contacting is sufficient to result in frothing of the reaction product.