Flame retardant phosphonate additives for thermoplastics

A flame retarded thermoplastic resin composition comprising a phosphonate having flame retardant properties, said phosphonate having the general formula

• wherein
• R1 and R2 are independently C1–C4 alkyl,
• R3 is H or C1–C4 alkyl, and
• R4 is linear or branched C9–C22 alkyl, C9–C22 cycloalkyl, C9–C22 aryl or C9–C22 aralkyl and
• n=0or 1.

A method of producing a flame retardant phosphonate composition of the general formula (IV):

• wherein
• R1 and R2 are independently C1–C4 alkyl,
• R3 is H or C1–C4 alkyl, and
• R4 is linear or branched C9–C22 alkyl, C9–C22 cycloalkyl, C9–C22 aryl or C9–C22 aralkyl and
• n=0 or 1:
• wherein said method comprises the steps of:
• 1) first reacting trimethylolalkane of general formula (I), wherein R3 is H or C1–C4 alkyl with a phosphite of the general formula P(OR)3, wherein R is alkyl, aryl or aralkyl, in a molar ratio sufficient to produce a cyclic phosphite of general formula (II)
• 2) second reacting said cyclic phosphite of the general formula (II) with a phosphonate of general formula (III),
• wherein R1 and R2 are independently C1–C4 alkyl and R4 is linear or branched C9–C22 alkyl, C9–C22 cycloalkyl, C9–C22 aryl or C9–C22 aralkyl, in a molar ratio sufficient to produce said flame retardant phosphonate composition of said general formula (IV).