The raw material of the bamboo pulp paper tray is only about 1% of the pulp of paper fiber. After the wet paper is formed, the moisture content of the wet paper must be reduced to 55% by the mechanical extraction method, and the moisture content of the paper tray is 65%-75 after forming. %, it is difficult to use mechanical methods to reduce the water content.
In the production process of the paper tray, about 3.5-4.5KG of water is removed for every kilogram of bamboo pulp paper tray finished product through the drying process. Therefore, drying is an important process in the production of paper trays. The production cost of the drying process occupies a large proportion in the production of paper trays. Increasing the drying efficiency of paper trays is a key measure to increase the production efficiency of paper trays.
The wet paper mold with paper fiber as the main component is a porous object with capillary structure inside. Moisture exists between the surface of the fiber and the pores of the fiber capillary. The paper support products used for the inner packaging of products generally require good dynamic cushioning properties, and the moisture in them cannot be removed by mechanical extraction, but needs to be removed by drying. Therefore, compared with the conventional paper drying process, the drying strength of the pulp molded product is very large. On the one hand, hot air acts as a heat source to provide energy for evaporating moisture, and on the other hand, it acts as a moisture carrier to take away the evaporating moisture.
The moisture in the wet paper tray depends on the internal and external diffusion of moisture. The so-called internal diffusion refers to the migration process of water in the wet paper tray from the inside to the outer surface; the external diffusion refers to the moisture being carried away from the surface after evaporation. The process of walking. The dryness rate of the paper support depends on the speed of the internal and external diffusion of the moisture and the balance and coordination between the two. The reasonable process conditions should be formulated around the above two aspects and the dry physical properties of the paper support product.
After the bamboo pulp paper support product is vacuum-adsorbed and formed, there are three forms of water in the wet paper fibers: bound water, adsorbed water and free water. The purpose of drying the paper tray product is to remove the free moisture in it, so that the bamboo pulp paper tray can reach the equilibrium moisture content.
The paper tray drying mechanism is that when the water vapor pressure on the surface of the wet paper tray is greater than the partial pressure of the water vapor in the drying medium, the moisture on the surface of the wet blank will continuously vaporize and enter the air, and the moisture in the wet blank will continue to diffuse to its surface. The speed of vaporization and diffusion varies with the temperature of the medium, the moisture of the wet blank, the thickness and size of the paper support, and so on.
