Metal salts of modified anhydride resin

A metal salt of an anhydride-modified resin prepared by the method which comprises reacting in an aqueous medium (A) about 0.4 to about one equivalent of a water soluble salt selected from chlorides and nitrates of metals selected from zinc, aluminum, lead and cobalt andmone equivalent of (B) the sodium or potassium salt of the half acid/half ester of said anhydride-modified resin;

• where said half acid/half ester salt is prepared by (1) reacting said anhydride-modified resin to reduce its acid number about 40-60 percent with an alcohol selected from methanol, ethanol, isopropanol, n-butanol and isooctyl alcohol and (2) reacting the product thereof as a mixture with an aqueous solution of about 75 to 110 stoichiometric percent of a hydrozide selected from at least one of sodium hydroxide and potassium hydroxide;
• where said anhydride-modified resin is comprised of about 45 to about 55 mole percent units derived from maleic anhydride and, correspondingly, about 55 to about 45 mole percent units derived from a piperylene/methyl branched monoolefin backboned resin comprising about 40 to about 70 weight percent units derived from piperylene and correspondingly about 60 to about 30 weight percent units derived from at least one methyl branched .alpha. or .beta. monoolefin containing 4 to 6 carbon atoms, where the weight ratio of piperylene to said branched monoolefin is in the range of about 0.8/1 to about 2/1.