Improved flatness in corrugated board production practices (2)

Qualitative analysis

The above test results show that the paper, the quantitative, and the moisture content are different, and its shrinkage is also different. This is an important physical property of the paper. With the same paper material in the face, the cardboard can easily achieve a good flatness, and vice versa. To comprehensively consider the changes of the above five major factors, make appropriate adjustments. The goodness of flatness depends on the shrinkage of each layer of the paper. To make the paperboard have a better flatness, the shrinkage of the paper must be basically the same, and the most important one is the paper in the surface. The shrinkage of the tissue paper is smaller than that of the paper and it is a negative arch. On the other hand, the local unevenness of the paper shrinkage becomes positive and negative arch. From the analysis of the process of board formation in the production line, the control shrinkage rate can be divided into two stages.

(1) The formation of corrugations. This is the key step for controlling the shrinkage rate, which is the various processes before feeding the raw paper to the secondary coating. According to the actual conditions of the paper, steam pressure, ambient temperature, and humidity in each layer of the tile, adjust the preheating temperature, the length of the heated surface (wrapping angle), the method of ventilating the moisture, the steam spray, and the amount of glue. The technical parameters of the production line speed allow all layers of paper to be controlled through appropriate and effective processes, and each of them is free to shrink. The final shrinkage rate is basically the same.

(2) The cardboard forming stage. It is the bonding, drying and ironing of the secondary coating to the subsequent process. At this point, each layer of paper has not been able to shrink freely. After being glued into cardboard, the shrinkage of each layer of paper is restricted by each other. The bonding point can be said to be the starting point of cardboard arching. To select and adjust the technical parameters such as the amount of glue, the temperature of the baking board, and the speed of the production line, control the difference in shrinkage ratio to the minimum, and iron the arches generated by the cardboard as much as possible.

Improvement of Corrugated Board Flatness

First, the base paper provided by the supplier is required to have a qualified and stable basis weight and moisture content. During transportation and loading and unloading, rain is prevented from getting wet. The basic environmental humidity is maintained during storage in the factory.

The second is that the surface of the paper choice of materials as much as possible using the same type of paper or quantitative, moisture content, the same grade of paper.

Third, the paper with high water content is heated by the heating surface (wrapping angle) of the preheater, and the fan is used to ventilate the air to increase the time for releasing the water and slow the speed of the production line. The paper with a small water content is passed through a preheater (wrap angle). Heating surface length, natural ventilation, steam spray, speed up the production line.

Fourth, the amount of glue on each layer of paper remains the same, and the amount of glue on the entire width of the paper along the direction of the corrugation is even and moderate.

Fifth, pressure stability, traps and other pipe fittings to maintain normal function.

There are many factors that affect the flatness of corrugated paperboard. With the changes in the factors of flatness, improvements must be made according to local conditions, targeted, and the main contradiction should be resolved. The following examples illustrate common problems in producing single and double corrugated cardboard.

Cardboard is arched horizontally

Known: face paper is 250g/m2 A grade kraft paper, moisture content of 7.7%; (clamp) tile paper is 150g/m2 domestic high-strength corrugated paper moisture content of 10%; inside paper is 250g/m29B grade kraft paper, moisture content 14 %; air pressure 1.1Mpa/cm2 production line speed 60m/min.

ways to improve:

(1) The length of the heated surface of the (jaw) tile through the preheater (wrap angle) is increased by 1 to 1.6 times and 0.5 to 1.1 times, respectively.
(2) In the (clamp) tile line on the production line bridge moving at the use of 0.9KW medium speed ventilation, the workshop window ventilation.
(3) The face paper is evenly sprayed with a small amount of steam.
(4) The production line speed is reduced to about 50m/min.

Adjusted according to the above-mentioned selection parameters, the original transverse arch can disappear.

Cardboard from the longitudinal negative arch improvement method:

(1) Face paper increases the movement resistance in front of the three-layer preheater and increases the rotational force of the tube paper.
(2) The guide wheels and tensioning wheels of the Liwa paper in front of the three-layer preheater reduce movement resistance.

Appropriate adjustment of the original longitudinal arch can disappear.

(to be continued)