Cardboard sheet and process for producing the same

摘要

A corrugated fiberboard sheet includes three kinds of paperboards that are an outer paperboard, a corrugating medium and -an inner paperboard. Each of the paperboards includes a paperboard of not less than three layers of raw material mainly of wastepaper. All the layers of each of the paperboards are given a waterproofing treatment. The ratio of incorporation of a fungusproofing agent and positions of incorporation satisfy the conditions (1) the ratio of incorporation of the fungus proofing agent in the outermost layers of the outer paperboard and the inner paperboard being in the range of 1 to 4%, (2) the ratio of incorporation of the fungusproofing agent in the innermost layers of the outer paperboard and the inner paperboard being in the range of 0.5 to 4% and (3) the ratio of incorporation of the fungusproofing agent in the opposite outermost layers of the corrugating medium being in the range of 0.5 to 4%. The corrugated fiberboard sheet thus constructed can be advantageously used as a case like a tray for containing seedling pots which are used for raising the seedlings of plants, such as vegetables and flowers, for example.