| abstract |
A method of preparing a polyisocyanurate (PIR) foam, comprising: A) injecting into a closed mold cavity, wherein said mold cavity is at an absolute pressure of 300 to 950 mbar, a reaction mixture comprising : a) an organic polyisocyanate; b) a mixture of polyols, wherein the mixture of polyols comprises an aromatic poly (ester polyol), in which the aromatic poly (ester polyol) represents at least weight percent of the total amount of polyol; c) a trimerization catalyst; d) at least one flame retardant; e) optionally auxiliary substances; and f) a blowing agent component, wherein said reaction mixture has an isocyanate index greater than 250; and B) cure to form a polyisocyanurate foam. |