Grafting of chelating monomers to styrene—butadiene latexes



It has been previously reported that vinyl esters have been grafted to natural rubber latex. We have grafted two other types of vinyl monomers to styrene-butadiene latex. These monomers are the ammonium salts of acrylic acid and methacrylic acid, and the ammonium salts of vinyl chelating agents, such as N-(ar-vinylbenzyl)iminodiacetic acid. (Ionizing radiation doses of 0.5–2 Mrad are sufficient to accomplish the grafting.) These monomers, in the range of 2–6%, give very definite improvement in adhesion to metals. They also improve the rust resistance, and when pigmented with an iron oxide dispersion, improve the whitening resistance of the coating. The vinyl chelating monomers give the best improvement over the untreated latex, particularly in the resistance to whitening. The optimum amount of monomer is 4–6%. This compares very well with the theoretical amount for a monomolecular layer of monomer surrounding each latex particle.