| 摘要 |
A corrugated paper-board sheet with a single backing sheet has a moisture-resistant impregnant applied to the flat face and a waterproof starch adhesive applied to the crests of the corrugations. An impregnant is then applied, preferably by spraying, to the corrugated surface and an impregnated second facing sheet applied, which is then heated until the impregnant has completely and evenly penetrated at least the second facing sheet. The impregnant applied to the corrugations is preferably paraffin wax and that applied to the flat faces preferably wax containing a major proportion of rosin. The water-proof starch adhesive comprises 91% modified pearl starch, 7% resorcinol, 1% caustic soda and 1% formaldehyde, thinned with water. Specification 875,028 is referred to. |
