Ionomer resin, resin sheet, and laminated glass

A method of producing an ionomer resin, the method comprising:

• saponifying an ethylene-(meth)acrylic acid ester copolymer with a strong base;
• and
• demetallizing a saponification product obtained by the saponifying with a strong acid,
• wherein the saponifying and/or the demetallizing is/are performed in the presence of a transition metal,
• wherein:
• the saponifying and/or the demetallizing is/are performed using a reaction apparatus, and
• at least a portion of the reaction apparatus is formed of an alloy comprising nickel and chromium as transition metals in a total amount of not less than 50% by mass, and
• wherein the ionomer resin comprises:
• a (meth)acrylic acid unit (A);
• a neutralized (meth)acrylic acid unit (B);
• and
• an ethylene unit (C),
• wherein
• a total content of the unit (A) and the unit (B) is 6 to 10% by mole based on all monomer units constituting the ionomer resin, and
• the content of a transition metal in the ionomer resin is 0.01 to 100 mg/kg.