Low smoke, halohydrocarbon-compatible urethane-isocyanurate foam compositions

Claim 1

A composition curable by reaction with organic polyisocyanate to a polymer foam in which the predominant recurring polymer unit is isocyanurate, comprising I. a halogenated organic blowing agent; II. a polyester polyol mixture prepared by (a) transesterification, with a glycol of molecular weight from about 60 to about 400, of a residue remaining after dimethyl terephthalate and methyl p-toluate have been removed from the product of oxidation of p-xylene in the preparation of dimethyl terephthalate; or (b) esterification, with an alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and mixtures thereof, of a carboxyl functional residue resulting from the removal of terephthalic acid from the mixture obtained by the oxidation of p-xylene in the preparation of terephthalic acid; and III. a polyether polyol having an average hydroxyl functionality of at least 4 comprising the adduct of at least 4 moles of a C 2 -C 6 alkylene oxide and an organic compound selected from the group consisting of sucrose, methyl glucoside, pentaerythritol, sorbitol and mixtures thereof; said polyol mixture II containing both ethylene glycol or polyethylene glycol derivatives of said residue and sufficient higher alkylene glycol, or higher polyalkylene glycol derivatives of said residue to render said composition compatible without separation of said halogenated organic blowing agent and capable of use to prepare a foam with a Class I flame rating.