30
2020
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06
The use of PAM additives in white cardboard.
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1. Introduction to White Cardboard
Coated white cardboard is a high-end packaging material characterized by high technical content, high quality requirements, and great production difficulty. White cardboard is divided into single-sided coated white cardboard and double-sided coated white cardboard. Double-sided coated white cardboard is mainly used for packaging materials that require double-sided printing, such as exquisite greeting cards and advertising brochures. The pulp for white cardboard generally uses bleached sulfate wood pulp for the surface layer and bottom layer, while the core layer usually uses low-cost fibers to reduce costs. The quality of the core layer pulp must meet the following points: high bulk density, minimizing basis weight at a certain thickness; good formation and surface smoothness to lay a good foundation for the surface layer pulp and subsequent coating; sufficient interlayer bonding strength to prevent delamination; good drainage performance to ensure production speed and the operation performance of the paper machine; for food and liquid packaging products, the core layer pulp must also be odorless and tasteless. Bleached chemithermo mechanical pulp (BCTMP) fully meets the above requirements, thus gaining wide application in coated white cardboard. Since most of the lignin in the BCTMP used in the intermediate layer remains in the fiber, it can cause the fibers to harden relatively and resist cell cavity decomposition. At the same time, its hard tubular structure has a higher bulk density, which is usually worse than that of chemical pulp fibers.
2. Principle of Paper Strength Increase by PAM Dry Strength Agent The strength of the finished paper mainly comes from the strength and length of the fibers themselves, the beating condition of the pulp, the bonding (hydrogen bonds) between the fibers, and the surface sizing (such as surface starch) and spraying starch. Therefore, under certain conditions of pulp composition and beating, the bonding force between fibers determines the strength of the paper.
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