Introduction
In the process of producing corrugated cardboard, temperature has a great influence on the quality of corrugated cardboard. By controlling the temperature, we can adjust the moisture content of the corrugated base paper and control the curing time of the paste, so as to achieve the purpose of controlling the bonding speed and firmness of the corrugated paper. Therefore, temperature control is a very important link in the production process of corrugated paper and cannot be sloppy.
Why is Temperature Control Important in Corrugated Cardboard Production?
Temperature control is very important in the production of corrugated board because it can adjust the moisture content of the corrugated base paper and control the curing time of the paste, thereby achieving the purpose of controlling the bonding speed and firmness of the corrugated paper. Therefore, temperature control is a very important part of the corrugated paper production process. In order to effectively control the temperature, heaters and drying boards are set up in many places on the corrugated board production line. According to different situations, these parts should be adjusted at any time to ensure the smooth progress of production.
Temperature Control Challenges in Corrugated Cardboard Production
If the moisture content of the base paper is too high, it is necessary to adjust the paper guide roller to increase the base paper preheating wrap angle and increase the preheating area; if the moisture content is too low, the preheating area should be reduced, and the spray device on the single-sided machine may need to spray the base paper to increase the moisture content.
Single-sided corrugated cardboard is stored on the overpass for too long, thereby reducing the moisture content of the single cardboard. Therefore, it is necessary to reduce the accumulation of single-sided corrugated cardboard on the overpass conveyor belt.
The temperature of the double-sided machine directly affects the bonding and forming of the cardboard and the moisture content of the cardboard. It is necessary to change the temperature of the heating plate by adjusting the steam pressure entering the heating plate to ensure the production of high-quality corrugated cardboard. In addition, the length of the cooling section will also affect the moisture content of the cardboard. When the cooling section is too short, the moisture cannot evaporate in time, and the local air supply needs to be increased.
The drain device has an important influence on the temperature of the corrugated cardboard production line. If there is a problem with the drain device, such as damage to the suction pipe or incorrect installation position, it will affect the heating effect of the preheater and need to be repaired in time.
The production speed will also affect the temperature of the paper, that is, the speed should be reduced when the moisture content is too high, and the speed should be increased when the moisture content is too low.
The gap between the glue roller and the limit roller, the gap between the corrugating roller and the glue roller of the single-sided machine, and the gap between the pressure roller (touch pressure rod) and the glue roller of the double-sided machine all need to be precisely controlled to ensure uniform glue coating, which in turn affects the bonding quality and production efficiency of the paperboard.
Best Practices for Temperature Control in Corrugated Cardboard Manufacturing
Temperature control of single-facer unit
According to the analysis of tension during the corrugated board forming process, the moisture content of the base paper entering the single-facer is best between 9% and 12% during corrugation forming. According to this principle, the preheating roller on the single-facer and the preheating machine and spray device before and after the single-facer must be fully utilized to adjust the moisture content of the base paper.
If the moisture content of the base paper is too high, the movable paper guide roller of the preheating roller can be appropriately adjusted after the temperature of the preheating roller reaches the requirement, the preheating wrap angle of the base paper can be increased, and the preheating area can be increased, which can reduce the moisture content of the base paper to a certain extent. If the preheating area of the preheating roller is adjusted to the maximum and the moisture content of the base paper is still too high, the method of reducing the speed should be adopted to solve it.
When the moisture content of the base paper is too high, the preheating roller temperature that has been adjusted in advance may sometimes be reduced, so that the preheating requirements cannot be met. At this time, the steam supply pressure of the boiler should be appropriately increased under the premise of conditions permitting, so as to achieve the purpose of increasing the temperature of the preheating roller.
If the moisture content of the base paper is too low, the movable paper guide roller should be adjusted accordingly to reduce the preheating area. At the same time, the base paper should be sprayed with the spray device on the preheating roller and the single-sided machine to increase the moisture content of the base paper to meet the standard requirements. In addition, appropriately increasing the vehicle speed, thereby reducing the contact time between the base paper and the preheating roller in disguise, can also solve the problem of low moisture content to a certain extent.
The moisture content and temperature of the base paper should be measured at any time with a moisture meter, thermometer or pressure gauge, and adjusted according to the measurement results.
Temperature control of the dryer
The temperature of the dryer directly affects the moisture content of the final corrugated board. The heating plates of the dryer are generally three groups, each group consisting of four, five, and six heating plates. Each group of heating plates of the steam-heated dryer is equipped with a pressure regulating valve to adjust the steam pressure entering the heating plate, thereby changing the temperature of the heating plate to ensure the production of high-quality corrugated board. Among them, the following details need to be paid attention to.
Before entering the dryer, the moisture content of the single-faced corrugated cardboard will change due to the different storage time on the overpass. In addition, the moisture content of the paste liquid on the single-faced machine will also change after a period of use, which will cause the moisture content of the single-faced corrugated cardboard to change. Therefore, before the final compounding, the single-faced corrugated cardboard needs to be preheated twice.
The purpose of drying is first to ensure the solidification of the paste liquid and adjust the moisture content of the corrugated cardboard at the same time. The two cannot be neglected. Therefore, the pressure reducing valve should be adjusted at any time according to the moisture content of the single-faced corrugated cardboard to make the dryer reach the appropriate temperature, which can not only ensure the solidification of the paste liquid, but also ensure that the moisture content of the final corrugated cardboard is moderate. In addition, the length of the cooling section of the dryer also has a certain influence on the moisture content of the cardboard. When the cooling section is too short, the moisture cannot evaporate in time. At this time, it is necessary to increase the local air supply to achieve the purpose of drying.
If the ideal condition cannot be achieved through conventional temperature adjustment, you can try to adjust it by changing the speed of the vehicle. That is, slow down the speed when the moisture content is too high, and increase the speed when the moisture content is too low.
When the dryer is working, it cannot be stopped unless it is absolutely necessary. If the single-face machine in front needs to change the paper roll, the car can be driven faster before changing the roll to accumulate more single-faced cardboard on the overpass. After receiving the paper change notification, the dryer can slow down. If the dryer stops, the moisture on the cardboard on the dryer will evaporate completely, causing all the cardboard to be scrapped.
Impact of Temperature Control on Packaging Performance
Affecting the physical indicators and flatness of cardboard
The moisture content of cardboard directly affects the physical indicators of cardboard boxes and the flatness of cardboard, and is one of the biggest problems that cause cardboard cracking, cardboard bending, and poor cardboard bonding.
Affecting the moisture content of paper
In the process of producing corrugated cardboard, controlling the temperature of paper means controlling the moisture content of paper. The effect of relative humidity on the moisture content of paper is generally that the relative humidity increases, the moisture content of paper increases, and vice versa, the relative humidity decreases, and the moisture content of paper decreases. The effect of temperature change on the moisture content of paper is different. Generally, the temperature increases and the moisture content of paper decreases.
Affecting printing suitability and registration suitability
The size of paper moisture content is directly related to printing performance. For example, changes in paper moisture content can cause paper expansion and contraction (including local deformation). The dimensional stability of paper has a lot to do with the suitability and registration suitability of printing. Especially for products with multi-color overprinting, changes in paper size will cause product overprinting to be inaccurate, becoming defective or waste products.
Affecting the drying speed of ink
When the ambient temperature rises, the viscosity of ink decreases; when the ambient temperature decreases, the viscosity of ink increases. If the temperature is too low and the ink viscosity is too high, printing failures will occur, such as partial peeling of the paper surface and sticking to the rubber blanket or printing plate. Therefore, controlling the temperature and relative humidity of the printing workshop can control the drying speed of the ink and prevent printing failures.
Summary
Temperature control plays a vital role in the production process of corrugated board. Through effective temperature management, the moisture content of corrugated paper can be adjusted and the curing time of the paste can be controlled, thereby accurately regulating the bonding speed and firmness of the corrugated paper.