Hydrochloric Acid → HCID 17901426, compound

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Reaction Steps

Melamine pyrophosphate is conventionally prepared by heating an aqueous slurry of 2 moles of melamine in 4 moles of hydrochloric acid at 80°C to 90°C, forming a solution of melamine dihydrochloride. One mole of tetrasodium pyrophosphate is added, the temperature maintained for about 30 minutes, and the slurry quenched. The precipitated melamine pyrophosphate must be thoroughly washed to remove the by-product sodium chloride and dried. The process is described by Fessler in U.S. Pat. No. 3,914,193. However, the pyrophosphate ion is reported (Corbridge, D.E.C., Structural Chemistry of Phosphorus, Elsevier Scientific Publishing Co., New York, N.Y., 1974, p. 128) to decompose to orthophosphate at low pH and at elevated temperature, i.e., under the conditions necessary for the reaction between melamine dihydrochloride and tetrasodium pyrophosphate. At polymer extrusion temperatures that can exceed 300°C, melamine orthophosphate is less stable than melamine pyrophosphate. The presence of residual sodium and chloride ions also reduces the stability of melamine pyrophosphate under melt extrusion conditions.

Provenance & Evidence