Solutions for the inaccurate control of water in corrugated board

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.

After entering the dryer, first of all to ensure that the paste paste, and then according to the size of the water content, adjust the pressure reducing valve, so that it has the right temperature, so as to obtain the appropriate moisture content. Of course, the length of the cooling section of the dryer also affects the moisture content of the board. When the cooling section is too short, the water can be blown with a hair dryer if it cannot be distributed in a timely manner.

When the temperature adjustment fails to meet the desired requirements, it can be adjusted by changing the speed of the vehicle. If the water content is too high, you can slow down the car; when the water content is too low, you can increase the speed.

When the dryer is working, there is no last resort and no parking is allowed. When the front single-sided machine to replace the paper roller, before the roll change single-sided machine can be a little faster sports car, accumulating part of the single-sided cardboard on the flyover, the dryer received a paper change notification, you can run at a reduced speed, if the drying When the dryer stops, all the cardboard water on the dryer evaporates, causing the cardboard to be scrapped.

Affecting the temperature of the cardboard production line, in addition to whether the saturated steam supplied by the boiler reaches the specified pressure, the hydrophobic device of the steam piping system is also very important. Because the raw paper and single-sided paperboards pass through the preheaters, they need to take a lot of heat, and some of the saturated water vapor turns into condensed water. This part of the condensed water must be discharged in time, otherwise it will affect the preheating effect of the preheater.

Solution: If the preheating roller of the rotary steamer is used, a temperature paper or a temperature difference of more than 5°C at both ends indicates that the suction pipe is damaged or the mounting position is incorrect, and it should be disassembled for maintenance.

The trap is 2 to 3 times more hydrophobic than the condensate. If the amount of trapped water is not sufficient, the trap should be changed.

Check the drain outlet of the trap every week and clean it if it is clogged.

The quality of the paste, the size of the water, and the thickness have a great influence on the water content of the board.

If the paste has a large amount of water, a thin paste, a fast penetration, the water content of the cardboard is high. Conversely, the water content is small.

The solution is: strictly follow the times and ratio of the paste water and the mixing time to paste, master the viscosity of the paste. The viscosity of a general single-sided machine is 50 to 60 seconds, and that of a double-sided coating machine is about 100 seconds, and the double-sided coating machine should use the fresh paste made on the day. Only the production of good paste can produce qualified cardboard.

The amount of top paste affects the moisture content of the board

When the paste is the largest, the water content of the board is large, and the amount of water on the top of the board is small.

The processing method is as follows: For a single-sided machine, adjust the gap between the rubber roller and the rubber roller, the rubber roller and the main corrugating roller. Under normal circumstances, the gap between the rubber roller and the rubber roller is 0.2 to 0.25 mm, and the gap between the rubber roller and the main corrugating roller is generally 0.1 to 0.2 mm. Measured with a feeler gauge, both ends must be the same.

The gap between the squeegee and the squeegee of the double-sided gluing machine is 0.2 to 0.25 mm. The gap between the press roll and the top roll should be 0.05 to 0.1 mm lower than the height of the single-sided corrugated cardboard that is passed. The measurement method is to use a feeler gauge to measure the data at both ends. Whether it is a single-sided machine or a double-sided gluing machine, the width of the corrugated cardboard glue line produced is generally 1.5 to 2 mm.

As the rubber roller surface damage or foreign body caused uneven gluing, affecting the cardboard moisture uneven

The solution is: if the roller surface is worn or damaged, replace the rubber roller as soon as possible. If there is any foreign matter, it should be stopped immediately. All the rollers need to be cleaned every day after work, and foreign objects should be removed with a soft brush.

If the dryer conveyor belt is poor in breathability, or if water is sprayed on the conveyor belt at random, the water content of the board can be increased. The solution is: to analyze the cause of poor air permeability of the conveyor belt. If there is waste paper stuck, stop it immediately to clear it. If the big belt is used for a long time, it is necessary to replace the new belt. Do not spray water on the conveyor belt during use.

If there are too many single-sided paperboards on the single-sided conveyor belts on the flyover, the time is long and the water is distributed more, it is easy to cause the water content of the paperboard to be low.

The solution is: All operating stations across the board should always contact each other and take care of each other. The speed of operation should generally be unified. The storage capacity of the single machine board on the conveyor belts of each single-sided machine on the flyover can best account for 2/3 or 3/4 of the length of the conveyor belt.

Climate and environment will also have an effect on the moisture content of the board

In the high temperature and rainy season, the relative humidity is high, the flowability of the winter paste is poor, and the amount of upper paste is small, which will affect the moisture content of the cardboard.

The solution is: In the season with high temperature, increase the thermal area, reduce the spray, reduce the moisture content of the paste, increase the temperature, and make full use of the preheat roll to adjust the moisture content.

In short, there are many factors that affect the water content of the board, which requires the operator to strengthen their sense of responsibility. Everyone must do his or her own job. Carefully observe and carefully adjust to produce a qualified corrugated board. (Wen / Wang Hao)