摘要 |
Moisture-resistant packing cardboard of the corrugated type is prepared from flat paper sheets formed from 10% to 90% by weight of cellulose fibers and from 90% to 10% by weight of fibrils of at least one thermoplastic polymer and having a surface area greater than 1.0 m2/gm, by heating the sheets under pressure on an undulated surface and coupling the resulting corrugated or undulated sheets with one or more flat sheets to which the corrugated sheet is adhered through the tips of the corrugations or undulations. |