Rengo Co., Ltd.

Takeda Chemical Ind., Ltd.

Seiichi Igarashi

Masateru Tokuno

Toshiaki Hanyuda

Toshio Okada

Kazuo Kimura

Akira Ogino

Hideharu Ohtsuki

Kin-ichi Shirakawa

Hiroshi Inagaki

This invention relates to a method for preparing paper board having excellent wet tensile strength and compression strength, which comprises (a) having paper board impregnated or coated with a mixture of an unsaturated vinyl ester prepolymer having a molecular weight of 300 to 3000 and having at least one hydroxyl group at the .beta.-position with respect to an ester bond in the molecule with at least one monomer selected from the group of methylacrylate, ethylacrylate and butylacrylate in a mixing weight ratio of 10:90-40:60, and (b) irradiating the paper board having the resinous mixture with electrons to cure the resinous mixture.

Method for preparing paper board having improved wet compression strength

A paperboard impregnated with polyurethane resin having specific NCO content and average molecular weight at the rate of 0.05 to 5.0 weight percent relative to the paperboard has excellent mechanical properties such as compressive strength, tensile strength, tearing strength, folding endurance, etc., even in wet state.

Paperboard impregnated with polyurethane resin

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Suita, Japan

Seiichi Igarashi