Method for increasing melt flow of a bimodal ionomer composition

A method of providing a trimodal ionomer composition having an increased melt index compared to a similar ionomer composition consisting essentially of the corresponding high molecular weight acid terpolymer, high molecular weight acid dipolymer and low molecular weight acid copolymer containing carboxylate salts with cations of a single element, said method comprising the steps of providing

• (a) 20 to 80 weight %, based on the combination of (a), (b) and (c), of an E/X/Y terpolymer wherein E represents copolymerized units of ethylene, X represents copolymerized units of a C3 to C8 α,β-ethylenically unsaturated carboxylic acid, and Y represents copolymerized units of a softening comonomer selected from the group consisting of vinyl acetate, alkyl acrylate and alkyl methacrylate, wherein the alkyl groups have from 1 to 8 carbon atoms, wherein the amount of X is from about 2 to about 30 weight % of the E/X/Y terpolymer, and the amount of Y is from 3 to about 45 weight % of the E/X/Y terpolymer, and wherein the weight average molecular weight (Mw) of the E/X/Y terpolymer is in the range of 80,000 to 500,000 Da;
• (b) 5 to 75 weight %, based on the combination of (a), (b) and (c), of an E/W dipolymer wherein E represents copolymerized units of ethylene and W represents copolymerized units of acrylic acid or methacrylic acid, wherein the amount of W is about 3 to about 25 weight % of the E/W dipolymer and wherein the weight average molecular weight (Mw) of the E/W dipolymer is in the range of 80,000 to 500,000 Da;
• and
• (c) 2 to 20 weight %, based on the combination of (a), (b) and (c), of an E/Z copolymer wherein E represents copolymerized units of ethylene and Z represents copolymerized units of acrylic acid or methacrylic acid, wherein the amount of Z is about 3 to about 25 weight % of the E/Z copolymer and wherein the weight average molecular weight (Mw) of the E/Z dipolymer is in the range of 2,000 to 30,000 Da;
• combining the E/X/Y terpolymer, the E/W dipolymer, and the E/Z dipolymer;
• and
• neutralizing at least 35% of the combined acidic groups in the E/X/Y terpolymer, the E/W dipolymer and the E/Z dipolymer to form carboxylate salts comprising a combination of zinc cations and cations of one or more elements selected from the group consisting of group IA elements and group IIA elements;
• provided that when X represents copolymerized units of acrylic acid and W represents copolymerized units of methacrylic acid, in an amount greater than 12 weight % of the E/W copolymer, the group IA element is other than sodium and the group IIA element is other than magnesium.