The strength of corrugated board directly affects the compressive strength of corrugated boxes. Excluding the factors affecting the strength of the corrugated board, the key factor of the corrugating medium's ring pressure index is the control of moisture in the corrugated board production process. For the control of the water content of corrugated board, the author believes that the following aspects should be controlled.
Control the moisture of corrugated paper
1. The moisture content of the corrugated paper into the factory should be strictly inspected in accordance with GB13023-91.
2. After entering the factory, the storage temperature of the corrugated paper should be controlled at room temperature and the relative humidity should not exceed 40%.
3. The corrugated paper should be stored stacking vertically, and the ground should be protected against moisture.
4. The storage time of corrugated paper should not be too long. Controlling the temperature and temperature of the corrugated board production process is an important condition for directly adjusting the moisture content of the corrugated paper and ensuring the adhesive paste. Therefore, when the corrugated cardboard production line is between 80 m/min and 120 m/min, the commonly used temperature should be controlled between 160°C and 180°C, and the saturated steam pressure of the boiler should be controlled between 0.9Mpa and 1.2Mpa. This can not only adjust the moisture content of the corrugated paper and single-faced corrugated board, but also ensure the gelatinization of the adhesive.
In order to ensure the strength and good adhesion of the corrugated board, the corrugated board should be adjusted according to the configuration of the corrugated board production line.
1. Corrugated molding is ideal for controlling the moisture content of corrugated paper entering a single-sided machine between 9% and 12%. When the corrugated paper moisture content is higher than the above indicators, it can be taken to increase the warm-up area or reduce the speed; when the corrugated paper moisture content is lower than the above indicators, spray can be taken to solve. The author believes that single-sided corrugated paperboard through the rapid transfer of paper on the bridge conveyor belt is positive ∞ type and consistent deposition distance, the original paper and corrugated paper moisture adjustment is better, the water content is more appropriate, single-sided corrugated cardboard stacked on the bridge The amount should not be too much, but in order to ensure that the double-sided machine does not shut down, the number of single-sided corrugated cardboard stacked on the flyover can be appropriately increased when the single-sided machine is changed paper.
2. The temperature of the dryer has a great influence on the water content of the corrugated board. The heating section of the corrugated board production line usually consists of three groups (four groups also). The number of heating plates is determined by the size of the heating plate and the speed of the corrugated board production line, and each group is provided with an independent control valve. To ensure that the moisture content of the single-faced corrugated cardboard before entering the dryer is basically the same, the size of the preheated area of ​​the single-sided corrugated cardboard on the triple preheater can be adjusted. The adjustment method is: when the water content is too high, the preheat area increases; when the water content is too low, the preheat area decreases.
3. As the corrugated board production process takes away a lot of heat, a part of the saturated steam will become condensed water in the preheater and the corrugating roll and can be discharged through the steam trap. In order to ensure the normal discharge of the condensed water, the author suggests that The bypass pipe valve before the steam trap is opened every 4 hours for 3 minutes to 5 minutes to ensure the temperature is relatively stable. Controlling the amount of glue used to make corrugated cardboard is usually done with a corn starch binder. Its main ingredients are: corn starch, water, sodium hydroxide and borax. Due to the different configuration of the corrugated board production line, the speed is different, and the adhesive is prepared. The viscosity, concentration, and gelatinization temperature are also different. With the amount of glue applied, the moisture content of the corrugated board will also change. When the amount of glue is large, the water content of the corrugated board is large, and vice versa. For the single-sided machine and the double-sided machine, the gap between the rubberizing roller and the rubber limiting roller is generally 0.2 mm to 0.25 mm; the gap between the single-sided machine and the rubberized roller is generally 0.1 mm to 0.2 mm; the double-sided machine pressure The gap between the roller (touch bar) and the rubber roller should be slightly lower than the single-sided corrugated board height of 0.05 mm to 0.1 mm. The gap can be measured using a feeler gauge, but the two rollers should be parallel to each other.
With the change of temperature and relative humidity (summer and winter), the amount of rubber applied is also low. The reason is that the viscosity of the adhesive in the summer becomes thin, and the concentration can be adjusted by appropriately increasing the solid content. The corrugated paper with a high hygroscopicity and a low cyclic pressure index is used. Adhesives have poor fluidity in winter and can improve the temperature of the adhesive to ensure good fluidity of the adhesive. In addition to the above-mentioned factors affecting the strength of corrugated board, the responsibility of operators is enhanced and the operator's skill level is improved so that each operator can observe carefully and carefully adjust and strictly operate according to the process requirements to produce high Quality corrugated cardboard.
Source: People and Packaging (Zhangjiagang) Co., Ltd.