How to Solve Paper Curl
The main reason for curling of the paper in the papermaking process is that the paper sheet itself has two sides, coupled with improper drying conditions during drying, unreasonable drying curves, inconsistent drying rates on both sides, and unbalanced shrinkage on both sides. Therefore, raw materials, papermaking processes, and environmental conditions can be adjusted.
Method of Solve Paper Curl
1. Raw material
– The ratio of slurry can be adjusted, and a slurry with a smaller coefficient of wet expansion can be selected;
– Decrease the beating degree of the pulp to reduce the coefficient of wet expansion of the sheet;
2. Forming
During the forming process, the internal structure of the sheet, especially the structure and composition of the two sides, is adjusted so that they tend to approach each other to reduce the tendency of curling. Can be adjusted based on practical experience.
– Adjust the pulp speed ratio;
– Adjust the outlets;
– Adjust the spray angle;
— Adjust the vacuum of the forming element;
– Adjust the dewatering capacity of the dewatering element;
– Adjust the performance parameters of the forming wire;
3. Pressing
Using a gradual increase in pressure to ease dehydration, a more uniform Z-sheet structure can be obtained. Such as shoe presses, keeping the upper and lower felts clean, are conducive to reduce the curl; choose the appropriate high roller.
4. Drying
The drying process is an important external factor that determines the degree of crimping. Adjusting reasonable process conditions can reduce the degree of curling.
– Properly reduce the speed difference of each transmission subdivision;
– Adjust the drying curve;
– Adjust the dry web tension appropriately;
– Adjust the Vac roller vacuum properly;
– Increase the smooth ventilation of hoods;
– Reduce the dryer sheet temperature;
5. Calender steam box
Calender steam box is a way to ease the curl of the sheet. Under the premise that the forming section and the drying section form latent curling, the steam box is used to uniformly spray the steam to rewetting the previously dried paper surface, reducing the stress-strain difference between the two sides, and the upper and lower sides of the paper sheet tend to be consistent to overcome the single row. But this is only a passive defense, and the practical application effect is not ideal. It should also eliminate its internal factors in the forming and drying department.
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