Reactive flame retardants blends for flexible polyurethane foams

1. A combustion modified flexible polyurethane foam, comprising a polyurethane resin, (a) a diester diol product having a viscosity of 15,000 to about 35,000 cps at 25° C. obtained by reaction of tetrabromophthalic anhydride, diethylene glycol and propylene oxide in a single stage process in the absence of an organic solvent, and (b) at least one epoxy resin comprising at least one cycloaliphatic epoxide, wherein the proportions by weight of components (a) and (b) are in the range of about 98.5:1.5 to about 96.5:3.5,

wherein the combustion modified flexible polyurethane foam has a density in the range of 16 kg/m 3 to 25 kg/m 3 and uniform permeability that is characterized by a maximum variance in air flow of less than 0.5 standard cubic feet per minute (SCFM) determined by measuring the maximum airflow difference between 3 random measurements over a 50×50×25 mm sample of the combustion modified flexible foam, and wherein the diester diol product is present in the final formulated resin at from 5 to 15% by weight.

2. The flexible polyurethane foam of claim 1 , which further comprises (c) at least one hindered phenolic anti-oxidant in which the phenolic ring is substituted by at least one alkanoic alkyl ester group in which the alkanoic acid moiety has from about 2 to about 4 carbon atoms and the alkyl moiety has about 6 to about 16 carbon atoms, wherein the proportions of (c) to (a) plus (b) are in the range of about 0.1:100 to about 1:100.

3. The flexible polyurethane foam of claim 1 , wherein component (b) comprises at least one epoxycyclohexane ring.

4. The flexible polyurethane foam of claim 3 , wherein component (b) is 3′,4′-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

5. The flexible polyurethane foam of claim 2 , wherein component (c) is 3,5-Bis(1,1-dimethylethyl)-4-hydroxy-benzenepropanoic acid, C 13-15 alkyl ester.