Refractory thermal insulation materials for microwave heating furnace

The present invention relates to a refractory heat-insulating material for a microwave furnace in which baking materials are calcined by self-heating proceeding from irradiation of microwave. The refractory insulating material consists of a heating layer and a foundation material. The heating layer is located on one surface of the foundation material. The heating layer is located on one surface of the foundation material. The heating layer mainly comprises mullite particles and inorganic binders, and the foundation material mainly comprises inorganic fibrous materials. It is essential in the heating layer that the mullite particles are covered with the inorganic binders continuously like film. The heating layer comprising particles having the higher microwave absorption characteristic than mullite particles is more preferable. The heating layer comprising organic binders is more preferable. It is more preferable in the heating layer that the mullite particles and the particles having the higher microwave absorption characteristic than mullite particles are covered with the inorganic binders continuously like film.