Method for improving the rigidity of the cardboard core structure ply cardboard core, and cardboard core, made of the structure plies

摘要

A structural ply of a spiral paperboard core has an elasticity modulus E in the cross machine direction (CD) higher than 4500 Mpa, and an elasticity modulus E in the machine direction (MD) higher than 7500 MPa (N/mm2). Such paperboard cores may be manufactured by using, either solely or partly, these structural plies, the paperboard for making up such structural plies having been manufactured by press drying. Paperboard based on the press drying method can be manufactured, e.g., with a board machine employing the Condebelt process. The cores may be used as yarn carriers and as tubes for thin films and foils, which may be wound onto and unwound from the cores at a speed of at least about 200 meters/minute.