Patent ID: 7683135

Claim:
An ethylene-vinyl alcohol based copolymer, comprising: ethylene units (III), vinyl alcohol units (IV), and vinyl ester units (V), wherein the proportion of the ethylene units (III) with respect to the total of the units (III+IV+V) ranges from 20 to 60 mole %, and the proportion of the total (I+II) of carboxylic acids units (I) and lactone ring units (II) in copolymer terminals with respect to the total (III+IV+V) of the units is 0.12 mole % or less, the respective units (I) through (V) represented by formulae: where X is a hydrogen atom, a hydroxyl group, or an esterified hydroxyl group, Y is a hydrogen atom, an alkali metal, or an alkaline earth metal, and R is a linear or branched alkyl group, and wherein the ethylene-vinyl alcohol based copolymer conforms to the expression G< 1.53−0.0239×Eu where G is a numerical value representing the content of 1,2-glycol units, expressed as mole %, and Eu is a numerical value representing the proportion of the ethylene units (III) with respect to the total (III+IV+V) of the ethylene units (III), the vinyl alcohol units (IV), and the vinyl ester units (V), expressed as mole %.