Patent ID: 8399096

Claim:
A precursor acid copolymer comprising: (A) copolymerized units of ethylene and about 20 to about 30 wt %, based on the total weight of the acid copolymer, of copolymerized units of an α,β-ethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid; wherein (B) the precursor acid copolymer has a melt flow rate of about 10 to about 4000 g/10 min, as determined in accordance with ASTM D1238 at 190° C. and 2.16 kg; and wherein (C) said precursor acid copolymer, being neutralized to a level of about 40% to about 90% based on the total number of the carboxylic acid groups present in the precursor acid copolymer, produces a sodium ionomer, said sodium ionomer comprising carboxylate groups and counterions, said counterions consisting essentially of sodium cations, and wherein the sodium ionomer has a melt flow rate of about 0.7 to about 25 g/10 min and a freeze enthalpy that is not detectable or that is less than about 3.0 j/g, as determined by differential scanning calorimetry in accordance with ASTM D3418.