The invention relates to a novel method for preparing a
styrene-
acrylate copolymer emulsion used in antirust primer paint. The method comprises steps that: (1)
phosphate ester functional monomers are subject to a
polymerization reaction; two hydroxyl groups of each
phosphate ester group are subject to a
chelation reaction on the
metal surface, such that a dense
phosphate ester (salt) protective film is formed on the
metal surface, and water molecules and other salt ions are prevented from contacting the
metal; the introduced phosphate ester group assists in improving the adhesion of painted coatings on metal surfaces, and in improving the antirust capacity of the painted coatings; (2) diacetone
acrylamide (DAAM) and
adipic dihydrazide (ADH) form a cross-linking
system of the antirust
emulsion; hydrazine groups in hydrazino-(NH2-NH2) and
ketone groups in the DAAM (C=O) are subject to a
dehydration condensation reaction, wherein the
ketone groups are copolymerized on the
copolymer; through outer cross-linking, a
emulsion film with a three-dimensional reticular structure is obtained; (3) an emulsifying
system is formed by combining a reactive anion emulsifier and a non-
ion emulsifier, such that problems of emulsion deposition and gelling are solved. With the method provided by the invention, an aqueous emulsion with a high
solid content is prepared, and
water resistance and
weathering resistance of the antirust paint is improved.