Method for improving the bending quality of water resistant corrugated paperboard

Claim 1

The method defined in claim 1 wherein said corrugated paperboard is impregnated with said solidifiable material by dipping said paperboard in a liquid reservoir of said material maintained above its melting point.

Claim 3

A method for forming a flexible fold in a sheet of water-resistant corrugated paperboard, which comprises: impregnating said corrugated paperboard by dipping said paperboard in a liquid reservoir of molten waterproofing agent selected from the group consisting of wax and wax-polymer compositions; and thereafter forming a score line on said paperboard at a desired fold by compressing said paperboard along said desired fold line sufficiently to exceed the yield strength of said paperboard, thus causing a permanent deformation of said paperboard along said fold line, said paperboard being maintained at an elevated temperature during the scoring operation.

Claim 4

A method of manufacturing self-enclosing water-resistant corrugated paperboard boxes, which comprises: cutting a corrugated paperboard to obtain a substantially rectangular box blank; forming a plurality of slots at either side of said blank extending from the outer edge of said blank inwardly a distance equal to the desired flap width so as to define four flaps at each side of said blank, each of said slots situated opposed to a corresponding slot in said other flap section; impregnating said corrugated paperboard by dipping said paperboard in a liquid reservoir of molten waterproofing agent selected from the group consisting of wax and wax-polymer compositions and draining excess impregnant therefrom; thereafter forming two parallel spaced flap score lines normal to the flutes of said corrugated paperboard and extending the length of said blank at the desired flap folds, said flap score lines defining outer spaced flap sections and an intermediate panel section theRebetween; folding said blank so that the two opposite ends of said panel section are mated; and fastening said panel section at the mated ends to form a collapsed box shell.