Abstract: The problem to be solved by the invention is to provide an ionomer having excellent transparency, maintaining a high elastic modulus at high temperatures, being less coloration, and having a reduced odor during molding processing. The means for solving the problem is an ionomer comprising 0.05 to 1.0 mol % of (meth)acrylic acid ester units, 4.5 to 9.0 mol % of carboxylic acid units, 0.65 to 3.0 mol % of carboxylic acid neutralized product units, and ethylene units, based on the total monomer units which constitute the resin, with the total content of the (meth)acrylic acid ester units, the carboxylic acid units, and the carboxylic acid neutralized product units being 7.0 to 10 mol %.

Abstract: It is an objective of the present invention to provide a composite sheet and a production method thereof, which composite sheet has excellent sealing ability, since the sheet exhibits high compressibility and yet low stress relaxation, as well as high strength and excellent pressure resistance. The objective of the present invention is also to provide a sheet gasket having the above-mentioned properties. The composite sheet according to present invention is characterized in that pores of an expanded porous PTFE sheet are filled with silica gel; and a ratio of remaining pores is not less than 5% and not more than 50%.