Process for the preparation of N-phosphonomethyl glycine

Claim 2

A process for the preparation of N-phosphonomethyl glycine, wherein glycine is dissolved in an alcoholic solution of formaldehyde and a tertiary base, to the so obtained completed solution a dialkyl phosphite is added, the reaction mixture is subjected to an alkaline hydrolysis followed by an acidification whereupon the desired N-phosphonomethyl glycine is obtained by precipitation.

Claim 3

The process of claim 1 comprising the following steps: Dissolving formaldehyde in an alcohol with heating and adding a small quantity of a tertiary base to effect the depolymerization of the paraformaldehyde; adding glycine and a greater amount of said tertiary base; adding after completion of the solution, a dialkyl phosphite; reacting the mixture in the heat and saponifying the formed ester by means of an aqueous NaOH solution while removing said alcohol and said tertiary base; and acidifying the obtained alkaline solution in order to precipitate said N-phosphonomethyl glycine.

Claim 4

The process of claim 1 or 2 wherein said alcohol is methanol, said formaldehyde is trioxymethylene or paraformaldehyde, and said tertiary base is triethylamine.

Claim 5

The process of claim 1 or 2, wherein the acidification of the final alkaline solution is effected to a pH of less than 2.

Claim 6

The process of claim 3 wherein a solution of triethylamine in methanol is obtained by the recuperation and the recycling of a distillate at a temperature of not more than 70° C. of said aqueous alkaline saponification solution of the process.

Claim 7

The process of claim 1 or 2, wherein the molar ratio of triethylamine to glycine is not less than 1, the ratio of formaldehyde; to glycine is comprised in the range between 1 and 2 and the ratio of said phosphite to said glycine is comprised in the range between 0.4 and 2, the amount of solvent is between 150 and 500 ml per mol of glycine, the amount of NaOH to hydrolyze the ester is comprised between 3 and 4 mols per mol of said phosphite used and the amount of acid necessary to effect the acidification of the saponified solution corresponds to the molar amount of said NaOH.

Claim 8

The process of claim 1 or 2 wherein hydroxymethylphosphonic acid is reclaimed as a secondary reaction product.

Claim 9

The process of claim 7 wherein the reclaiming of said hydroxymethylphosphonic acid is carried out in the form of an insoluble salt before or after the separation of said N-phosphonomethyl glycine.

Claim 10

The process of claim 6 wherein the ratio of formaldehyde to glycine is between 1.3 and 1.6, the ratio of phosphite to glycine is between 0.6 and 1.6 and the solvent is methanol.

Claim 11

The process of claim 8 wherein the insoluble salt is calcium salt.