Cross Direction Crease Matrix Channel Geometry Tuning for Chemical Pulp
Cross direction creasing of chemical pulp requires expanding matrix channel width to 1.5 to 1.7 times board caliper plus rule width to prevent liner cracking.
Solid Unbleached Board
Fiber Structure
Multi-ply paperboard grades manufactured primarily from unbleached chemical wood pulp offer high strength and a natural brown appearance. This solid unbleached board is often used for heavy duty packaging where tear resistance is more important than a white printing surface. It contains a high proportion of long virgin fibers.
The material typically features a thin mineral coating on the top side to allow for high quality graphics.
Mechanical Strength
Internal bonding strength allows this grade to withstand the rigors of frozen food environments and beverage carrier applications. Because solid unbleached board does not undergo the bleaching process, the lignin remains in the fibers and provides additional stiffness. This makes the board less prone to bulging when filled with heavy contents.
It maintains its structural integrity even when exposed to high humidity.
Application Range
Recycling circuits accept this material easily because of its high quality virgin fiber content. While solid unbleached board is more expensive than recycled grades, its performance allows for lower basis weights to achieve the same box compression strength. It provides a barrier against moisture and grease when treated with functional coatings.
The brown aesthetic supports brands seeking a perception of environmental responsibility. Production occurs on large fourdrinier machines equipped with multiple headboxes.