Corrugated paperboard and its method of manufacture

摘要

This invention relates to a method of producing corrugated paperboard which is coated with a thermoplastic material which serves to bond the corrugated medium to one or more corrugated facing sheets and the corrugated paperboard produced by this method. The liners and medium which form the corrugated paperboard are sized to inhibit water wicking tendencies. The entire surface area of each surface of the medium is coated with a layer of thermoplastic material and the entire surface area of each liner is coated with a layer of thermoplastic material. The medium is continuously corrugated between a first and second pair of meshing corrugated rollers at a temperature sufficient to mold the medium to the corrugated configuration and retaining the corrugated medium on the second corrugated roll between two points spaced apart by a first annular arc around the periphery of the second roll and bringing the continuously advancing web of the first coated liner into contact with the corrugated medium whereby the coated inner surface of the liner presses against the peaks of the flutes of one of the corrugated coated surfaces of the coated medium. Intense heat is continuously directed against the thermoplastic coating of the inner surface of the first coated liner to render the surface tacky and bondable. The first coated liner is maintained in contact with the peaks of the flutes of the corrugated medium over an arc of rotation of the corrugated roller for a period of time sufficient to permit the thermoplastiic material to harden before the medium with the liner bonded to one side thereof emerges from contact with the second corrugated roller, thereby forming a single-faced corrugated paperboard. The single-faced corrugated paperboard is removed from contact with the second corrugated roller and brought into contact with the continuously advancing web of a second coated liner so that the peaks of the flutes of the remaining unlined corrugated coated surface of the single-faced corrugated paperboard engage the second liner. Heat is again directed to the thermoplastic coating of the inner surface of the second coated liner prior to its contact with the peaks of the flutes of the corrugated medium. The second coated liner is maintained in contact with the peaks of the corrugated medium for a period of time sufficient to permit the thermoplastic material to harden and thereby bond the second liner to the medium to form a water-resistant, warp-free, corrugated paperboard.