1、 Introduction to white cardboard

Coated white cardboard is a high-grade packaging material, which has the characteristics of high technical content, high quality requirements and difficult production. White cardboard can be divided into single-sided coated white cardboard and double-sided coated white cardboard. Double-sided coated white cardboard is mainly used for packaging materials requiring double-sided printing, such as exquisite greeting cards, advertising brochures, etc. Bleached kraft wood pulp is generally used for the surface and bottom layer of white cardboard. In order to reduce the cost, low-cost fibers are generally used for the core layer. The quality of core layer slurry must meet the following points: high loose thickness, reduce the quantity as much as possible under a certain thickness; Good forming and surface smoothness, laying a good foundation for surface slurry and subsequent coating; Have sufficient interlayer bonding strength to prevent delamination; Good water filtering performance to ensure production speed and operation performance of paper machine; For food and liquid packaging products, the core slurry must also be odorless and tasteless. Bleached chemithermo mechanical pulp (BCTMP) fully meets the above requirements, so it has been widely used in coated white cardboard. Because most of the lignin of BCTMP used in the middle layer remains in the fiber, the fiber will be relatively hardened and resistant to cell cavity decomposition. At the same time, its hard tubular structure has a high loose thickness, which is usually worse than that of chemical pulp fiber.

2、 Paper force increasing principle of PAM dry enhancer

The strength of the paper mainly comes from the strength and length of the fiber itself, the beating of the slurry, the (hydrogen bond) bonding between the fibers, as well as the surface sizing (surface starch, etc.) and spray starch. Therefore, when the pulp composition and beating conditions are certain, the bonding force between fibers determines the strength of paper.

3.Application of PAM dry enhancer in white cardboard

High gram weight social card or high loose thickness white card can effectively improve the interlayer bonding strength by adding PAM dry enhancer (about 7-15kg per ton of paper) to the core layer. Under the comprehensive adjustment of reducing the proportion of long fiber in the core layer, increasing the ash content in the core layer (increasing the amount of filler in the core layer) or the loose thickness of paper (increasing the proportion of self-made mechanical pulp), the interlayer bonding strength can be maintained at a high level, At the same time, it reduces the manufacturing cost of tons of paper and enhances the competitiveness in the same industry.