Process for producing ogranophosphorus ester compound and reactive flame retardant

A process for producing an organophosphorus ester compound characterized in that

• 1 a reaction mixture (M1) is produced by reaction of a dichlorophosphine derivative (a) of the general formula (1):
• R.sup.1 PCl.sub.2 (1)
• wherein R.sup.1 represents a hydrocarbon group having 1 to 18 carbon atoms with (meth) acrylic acid (b) said reaction is conducted in the absence of a catalyst and subsequently is esterified with a monool having 1 to 4 carbon atoms (c) to produce a reaction mixture (M2)
• 2 the resulting reaction mixture (M2) is neutralized with an alkali metal hydroxide or alkaline earth metal hydroxide (d) either in a solid form or in the form of an aqueous solution, wherein (d) is used in an amount corresponding to an equivalent ratio of hydrochloric acid in (M2)+unreacted (b) in (M2)/(d) in a range of 1/(0.8 to 1), and purified by phase separation or filtration to provide
• 3 a purified organophosphorus alkyl ester compound (A) of the following general formula (2). ##STR4## wherein R.sup.1 represents a hydrocarbon group having 1 to 18 carbon atoms;
• R.sup.2 represents hydrogen or methyl;
• R.sup.3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms;
• R.sup.4 represents an alkyl group having 1 to 4 carbon atoms.