Thermal stability of polyurethane-modified polyisocyanurate foam

Abstract

A polyurethane-modified polyisocyanurate (PU-PIR) foam exhibiting improved thermal stability is provided. The foam has incorporated therein a high molecular weight ammonium polyphosphate (APP). APP is employed as a partial or complete substitute for flame retardants conventionally employed in PU-PIR foams. The foams of the invention exhibit excellent and improved thermal stability characteristics as compared to foams to which no APP has been added.

1 . In a polyurethane-modified polyisocyanurate (PU-PIR) foam prepared from a reaction system comprising polyisocyanate, polyol, blowing agent, catalyst, surfactant and flame retardant selected from the group consisting of halogenated flame retardants, non-halogenated flame retardants, and mixtures thereof, the improvement comprising substituting at least about 33% of the flame retardant on a weight basis with high molecular weight ammonium polyphosphate having the general formula (NH 4 PO 3 ) n  wherein n is higher than 200, wherein the thermal stability of the ammonium polyphosphate-containing PU-PIR foam when measured at 800° C. under anaerobic conditions is improved by at least about 10% as compared to the thermal stability at 800° C. of a PU-PIR foam prepared under identical conditions as the ammonium polyphosphate-containing PU-PIR foam except for the substitution of ammonium polyphosphate. 
   
   
       2 . The PU-PIR foam of  claim 1 , wherein the ammonium polyphosphate is crystal phase II ammonium polyphosphate. 
   
   
       3 . (canceled) 
   
   
       4 . The PU-PIR foam of  claim 1 , wherein n is higher than 1000. 
   
   
       5 . The PU-PIR foam of  claim 1 , wherein from about 50% to about 100% of the flame retardant is substituted with ammonium polyphosphate. 
   
   
       6 . The PU-PIR foam of  claim 1 , wherein the ammonium polyphosphate represents from about 0.5 to about 10 weight percent of the PU-PIR foam, based on the total weight of the foam. 
   
   
       7 . (canceled) 
   
   
       8 . The PU-PIR foam of  claim 1 , wherein the flame retardant is selected from the group consisting of halogenated and non-halogenated phosphates, polyphosphates, phosphonates and polyphosphonates, and mixtures thereof. 
   
   
       9 . The PU-PIR foam of  claim 1 , wherein the flame retardant is a halogenated flame retardant or mixture of halogenated flame retardants. 
   
   
       10 . The PU-PIR foam of  claim 9 , wherein the halogenated flame retardant is a halogenated phosphate ester or mixture thereof. 
   
   
       11 . The PU-PIR foam of  claim 1 , wherein the flame retardant is a non-halogenated flame retardant or mixture of non-halogenated flame retardants. 
   
   
       12 . The PU-PIR foam of  claim 11 , wherein the non-halogenated flame retardant is a phosphate ester or mixture thereof. 
   
   
       13 . (canceled) 
   
   
       14 . The PU-PIR foam of  claim 1 , wherein the thermal stability of the ammonium polyphosphate-containing PU-PIR foam is improved by at least about 20%. 
   
   
       15 . The PU-PIR foam of  claim 1 , wherein the thermal stability of the ammonium polyphosphate-containing PU-PIR foam is improved by at least about 30%. 
   
   
       16 . The PU-PIR foam of  claim 1 , wherein the thermal stability of the ammonium polyphosphate-containing PU-PIR foam is improved by at least about 40%. 
   
   
       17 . The PU-PIR foam of  claim 1 , wherein the polyisocyanate is selected from the group consisting of aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates. 
   
   
       18 . The PU-PIR foam of  claim 1 , wherein the polyol is selected from the group consisting of polyester polyols, polyether polyols, polythioether polyols and mixtures thereof. 
   
   
       19 . The PU-PIR foam of  claim 1 , wherein the polyol is a polyester polyol. 
   
   
       20 . The PU-PIR foam of  claim 1 , wherein the polyol is derived from a natural fat  or oil.