Method for preparation of anti-calking coating with pigment therein

Abstract

A coating composition useful on a variety of substrates, and particularly as a coating for ammonium nitrate which exhibit a reduced tendency to cake or dust once applied to the surface of a substrate. In one embodiment, the composition is composed of magnesium stearate and an effective amount of magnesium oxide, i.e. 10-15% by total weight of the coating composition, to substantially minimize or reduce the tendency of the composition to cake or dust, particularly after the coating composition is applied to the substrate. The composition preferably is colored by incorporating pigment in a reactant mixture of stearic acid and magnesium oxide before completion of the reaction. As a result the pigment is entrapped in a matrix formed by the magnesium stearate and magnesium oxide so that discoloration by contact with the coating composition, for example on the coated substrate, does not readily occur. The reaction is conducted in two stages: in the first stage magnesium oxide, a relatively small amount of stearic acid, a reaction catalyst and water are mixed at about 750.degree. C. to uniformly disperse the magnesium oxide in the resultant slurry; then, in the second stage, the temperature is raised to 80.degree.- 85.degree. C. and the balance of the stearic acid is added and reacted to form the desired reaction product composition of the present invention. The pigment is added to the reaction mixture, preferably in the form of an aqueous surfactant solution, before completion of the reaction so as to become entrapped in a matrix formed by the magnesium stearate and magnesium oxide components of the reaction product composition.

Dependencies are inferred from the claim text.