Active ester curing agent compound for thermosetting resins, flame retardant composition comprising same, and articles made therefrom

An epoxy resin composition comprising a thermosetting resin and a phosphorus-containing aromatic polyester of formula (I) which is concurrently a flame retardant and an active ester curing agent

• where X is a bivalent aromatic hydrocarbon group containing from 6 to about 12 carbon atoms, and optionally substituted with an alkyl group or alkoxyl group, containing up to about 6 carbon atoms, or
• X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a bivalent linear or branched alkenylene group of from 2 to about 8 carbon atoms,
• Y is
• where Z is selected from the group consisting of a covalent bond, —SO2—, —C(CH3)2—, —CH(CH3)—, and —CH2—;
• a=0-2;
• b=0-2, and a and b are not both zero, and
• wherein the wavy lines of each structure of Y indicate the bonds to the O atoms which Y bridges in the general formula (I);
• R1 is, an alkyl group of from 1 to about 4 carbon atoms, phenyl, naphthyl,
• where R2 is —C(═O)R3 and where R3 is selected from an alkyl group of from 1 to 4 carbon atoms, a phenyl group, and a napthyl group
• and n is ≥1, and wherein the phosphorus-containing aromatic polyester of formula (I) is such that when it is reacted with the thermosetting resin, produces a product which does not contain any secondary hydroxyl groups.