The forming of white paper is mainly carried out by multi-circular mesh multi-drying cylinder paper machine or long circular mesh mixed paperboard machine. In the production process, the pulp is divided into multi-layer surface pulp, lining pulp, core layer pulp and bottom layer pulp. The surface pulp is the surface layer of the paper, which requires high whiteness and certain strength. It usually uses bleached sulfate wood pulp or some other pulps; the lining pulp plays an isolation role and also needs to have appropriate whiteness. Mechanical wood pulp or light-colored waste paper pulp is often used; the core layer pulp mainly plays a filling role, increasing the thickness and stiffness of the paperboard, and generally uses mixed waste paper pulp or straw pulp; the bottom layer pulp is used to improve the appearance of the paperboard, increase the strength and prevent curling, and high-yield pulp or better waste paper pulp is often used.
Taking the environmentally friendly blister double-sided coated white paperboard as an example, different pulps such as LBKP, DMOW, DIP, MW, BCTMP are first mixed in a certain proportion. Then the processes of impurity removal and screening, web forming, pressing and drying, surface sizing, hard calendering, coating, soft calendering and winding are carried out in sequence. In the web forming stage, each layer of pulp enters the headbox and is sprayed on the web. The amount of pulp hanging on each layer is controlled and compounded according to the setting, and then it enters the pressing and drying process to make the paper reach a certain dryness.
With the application of automation equipment and intelligent technology, the production efficiency of white paper has been greatly improved, and energy consumption has been effectively controlled. The introduction of environmental protection technology has also reduced pollution emissions in production. In the future, the white paper forming process will develop in a more efficient, environmentally friendly and intelligent direction, and the product will also move towards multifunctionality and personalization to meet market demand.