Water resistant corrugated paperboard

Claim 1

In the process of manufacturing water resistant corrugated paperboard, consisting of at least one linerboard component having both sides thereof coated with a film of thermoplastic material, and at least one corrugating medium component having both sides thereof coated with a film of thermoplastic material, the steps of: a. pretreating the said corrugating medium component .Iadd., before both sides thereof are coated with the film of thermoplastic material, .Iaddend.with an internal size treatment selected from the group consisting of 0.75- 1.0% rosin with about 1.5% alum, 0.2% stearic anhydride with 0.3-0.4% alum, or 0.2% succinic anhydride with 0.3-0.4% alum to inhibit the water wicking tendencies thereof; b. applying a direct pre-heat treatment to one side of the said coated and sized corrugating medium prior to entering the corrugating nip of a corrugating machine; c. applying an indirect pre-heat treatment to the opposite side of the said coated and sized corrugating medium by heating at least one of the corrugating rolls of the corrugating machine; d. applying a lubricating treatment in the form of a water spray or a water spray containing detergent to the corrugating nip of the corrugating machine; e. applying a direct pre-heat treatment to one side of the said coated linerboard component prior to entering the bonding nip of a corrugating machine; f. applying an indirect pre-heat treatment to the opposite side of the said coated linerboard component by heating the pressure roll of the corrugating machine; g. applying an additional direct heating treatment at the bonding nip of the corrugating machine to render the thermoplastic film surface on one of the components tacky and bondable; h. pressing the tacky and bondable surface of one of the components into contact with the other of said components at the bonding nip; and, i. cooling the laminate thus formed to allow the bond to set.