PURPOSE: To provide the titled material of high performance in both heat cycle and pressure cooker characteristics, comprising flexible liquid epoxy resin, filler, and curing agent, with its cured product limited in both contents of Na+ and Cl- ions.

CONSTITUTION: The objective sealing material comprising (A) 100pts.wt. of a liquid epoxy resin including flexible one (e.g., polybutadiene-modified epoxy resin), (B) pref. 20W30pts.wt. of filler (e.g., molten silica), and (C) a curing agent (an acid anhydride or aromatic amine) with its cured product containing ≤10ppm of Na+ ion and ≤300ppm of Cl- ion and having a Shore D hardness pref. 50W80. For limiting the contents of Na+ and Cl- ions, it is recommended that the resin A be purified to effect the contents of the Na+ and Cl- ions ≤1ppm and ≤500ppm, respectively.