Cardboard moisture content control and related matters needing attention

In the process of production of corrugated board, the moisture content of the board is very important. When the moisture is too high, the processed board will appear soft, not quite, easy to collapse after the box. When the moisture content is low, the processed cardboard is hard, brittle, and easily burst after being packed. The control of board moisture is a complicated matter, which is mainly determined by the following two factors:

The moisture of the raw paper entering the factory must be strictly controlled. According to the current standard, the moisture of the original paper delivery state should be (8±2)%. It is better to set up a separate warehouse for storing the base paper, the temperature is generally (18 ± 3) °C, and the humidity is generally (35 ± 5)%. Do not put it in the open air, otherwise it is easy to cause moisture changes and the two ends are not the same as the middle.

Temperature is one of the decisive factors affecting the quality of corrugated board. It can not only adjust the moisture of the base paper, but also increase the temperature of the base paper, which is an important condition for curing the paste liquid. Therefore, a large number of preheaters and flat-plate dryers are installed in the cardboard production line to adjust the moisture content of the base paper and the single-sided paper, and the paste is finally cured to achieve the purpose of bonding.

In order to effectively control the moisture of finished corrugated board, we must pay attention to the following issues:

If the moisture in the paperboard is too high and the temperature of the preheating roll does not meet the requirements, the steam pressure of the boiler must be increased so that the steam supplied can reach saturated steam. In general, the steam pressure should be kept at 1.1 MPa ± 0.2 MPa.

If the water content is low, it is necessary to adjust the paper guide roller to reduce the preheating area. At the same time, the single-sided on-machine spray device (wet roller) should be fully utilized to spray the base paper to increase the moisture content of the base paper to meet the standard requirements.

When the flat-plate dryers are working, they cannot stop when they have no other last resort. One-sided machine should speed up before replacing the base paper, and accumulate more paper on the bridge; the composite machine should decelerate after receiving the signal, and wait until the single-sided machine finishes the paper-feeding, and then speed up. If the equipment must be stopped in case of a failure, the conveyor felt should be raised to prevent excessive moisture loss from the board dryer.

For single-sided machines, adjust the gap between the squeegee and the squeegee. Under normal circumstances, the gap between the rubber roller and the rubber roller is 0.2mm to 0.25mm. The gap between the rubber roller and the main corrugating roller in the thermal state should be 0.02mm larger than the thickness of the corrugated paper used. For the double-sided machine, the gap between the scraper roller and the top roller is also 0.2mm to 0.25mm. The gap between the roller and the top roller should be 0.05mm to 0.1mm smaller than the height of the single-faced corrugated board. And the gap between both ends of the roller should be consistent and can be measured with a feeler gauge.

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