Method to Solve Inaccurate Control of Water Content in Corrugated Board (I)

In the production process, many people have encountered the problem of inaccurate control of the water content of corrugated board, problems of oversize (carton collapse, dew), or small (breaking of paperboard), and this issue is very important. .

This is mainly due to the fact that the control of the moisture content of the board is critical during the manufacture of the corrugated board. When the water content is too high, the processed corrugated board will appear soft and not quite. After the box is formed, it will cause collapse and dew. When the moisture content is low, the processed corrugated cardboard is hard and brittle, and it is easy to break after being put into a box. Therefore, only the strict control of the moisture content of corrugated board can produce high quality cardboard and cartons. Of course, the control of water contained in cardboard is a very complicated matter. It is determined by many factors, mainly including: The water content of the base paper for entering the factory must be strictly controlled in accordance with the provisions of national standards, the status of the delivery of base paper. The water content is generally 9% to 12%.

To adapt to this requirement, the solution is: First, a good quality, inspection of the moisture content of the base paper into the factory, requires the supplier to supply qualified raw paper. In addition, the base paper must be stored in a separate warehouse, the temperature is generally 15 °C to 20 °C, relative humidity is generally 30% to 40%. Do not put it in the open air, otherwise it will easily cause the change of the moisture content of the raw paper, and it will make the water content at both ends and in the middle inconsistent, which will bring more difficulties to the subsequent processing.

Temperature is one of the decisive factors affecting the quality of corrugated board

It can not only adjust the moisture content of the base paper, but also make the base paper have a certain temperature, which is an important condition for curing the paste liquid. Therefore, in a corrugated board production line, there are many preheaters and drying boards, which are used to adjust the moisture content of the base paper and single-sided paperboard, and to make the paste liquid to cure and bond the various layers of corrugated cardboard. The general speed is above 100m/min, and the paste curing temperature is usually 160°C to 180°C. In other words, the saturated steam pressure of the boiler should reach 0.9MPa to 7.4MPa.

Due to the need to process qualified corrugated board, it is necessary to go through different equipment, and different equipment in the formation of corrugated board, the impact on water content is different, the following separately stated:

Based on the analysis of the tension during the formation of a single-faced corrugated cardboard from a single-sided machine, we know that when corrugating, the moisture content of the single-sided machine base paper is 9% to 12%. According to this principle, we must make full use of the preheating roll on the single-sided machine and the preheater and sprayer before and after the single-faced machine to adjust the moisture content of the base paper.

The method is as follows: when the temperature of the preheating roller reaches the requirement and the water content of the base paper is too high, the movable guide roller of the preheating roller is adjusted, the preheating wrap angle is increased, the preheating area is increased, and the water content of the base paper is reduced. To meet the standard requirements. If the warm-up area of ​​the preheating roll is adjusted to the maximum, the moisture content of the base paper is still too high, and the method of reducing the vehicle speed may be adopted to solve the problem.

If the water content is too high and the temperature of the preheating roll does not meet the requirements, the steam supply pressure of the boiler must be increased so that the supplied steam reaches saturated steam, and the pressure reaches 0.9 MPa to 1.4 MPa.

If the water content is too low, it is necessary to adjust the movable paper guide roller to reduce the warm-up area, and at the same time, use the spray device on the preheating roller and the single-sided machine to spray the base paper to increase the moisture content of the base paper to meet the standard requirements. At the same time, the method of increasing the speed of vehicles can also be used to solve the problem of low water content.

The moisture content of the base paper and the temperature can be measured at any time using a water meter, a thermometer, or a pressure gauge, and can be adjusted at any time based on the results of the measurement. Of course, in addition to the instrument measurement, the "earth" method can also be used. According to our experience, if the single-faced corrugated paperboard on the overpass conveyor belt is in the positive ∞ shape, the adjustment of the moisture content of the base paper and the tile paper is relatively good, and the water content is also appropriate. When there is no thermometer, as long as spit saliva on the preheater, the saliva can be high in the preheater, then the temperature has exceeded 150 ~ C, it can be produced.

The temperature of the dryer has a great influence on the water content of the formed corrugated cardboard. As the dryer heating plate is generally divided into three groups, each group consists of four, five, six heating plates. Each set of heating plates is provided with a pressure regulating valve for adjusting the steam pressure entering the heating plate to change the temperature of the heating plate to produce a high quality corrugated cardboard.

The processing method is: Before the single-sided corrugated paperboard enters the dryer, due to the difference in the length of time that the single-sided cardboard is stored on the flyover, the water content changes, especially the moisture content of the paste liquid used on the single-faced machine has increased. In the triple preheater, the single-sided machine board must be warmed up. In the preheating process, according to the size of the water content, the movable guide roller should be properly adjusted to change the preheating area so that it can reach the appropriate moisture content.