[China Packaging Network News] First, cardboard warping
In general, there are six phenomena of warpage in corrugated cardboard. The most common ones are:
Warping
The reason for this is: the moisture content of the raw paper is too high (or the moisture content of the paper is low); the single-sided corrugated paper has too much water in the bond; the quantitative grades of the paper and paper are too different.
The solution: (1) increase the surface area of ​​the paper in the single cylinder dryer; (2) reduce the paper in the double layer preheater winding surface; (3) close part of the flat dryer steam valve; ( 4) Increase the running speed of the compound machine; (5) Reduce the gap between the scraper roller, the squeegee roller and the lower corrugating roller, and reduce the sizing amount of the single-faced corrugated roller; (6) Replace the liner paper that exceeds the moisture requirement.
2. Lateral warpage
The reason is: the moisture content of the base paper is too high; the temperature and speed of the heated area are not normal.
Solution: (1) increase the surface of the paper in the double-layer preheater heating surface; (2) the use of a better adhesive viscosity, reduce the amount of gluing machine; (3) reduce the single-sided machine paper (4) Reduce the production speed at the compounding machine; (5) Correctly adjust the line speed of the production line and match the steam valve of the flat dryer to match them; (6) Replace the tissue paper that exceeds the moisture requirement.
Second, cardboard false bonding
The so-called paperboard false bonding refers to a phenomenon that the paperboard can be stripped off from the back of the paper, paper and corrugated paper.
The main causes are: (1) the adhesive has insufficient viscosity or has deteriorated; (2) the speed of the corrugator or laminating machine is too fast; (3) the pressure of the corrugator is uneven or the corrugating roller is worn; (4) compounding Spreader rubber roller gap is too large; (5) paper moisture content is too high. Solution: (1) Improve and stabilize the adhesive quality. Relevant data suggest that the adhesive viscosity is generally 60S to 90S in winter and 90S to 120S in summer. The seven-layer box is generally about 305 times slower than the three-layer box; (2) It ensures that the steam pressure is 1.0MPa to 1.2MPa, and the temperature of each roller body and plate dryer is about 160°C; (3) The output of homemade corrugated roller is up to 3 million. When one meter is 3.5 million meters long, it must be replaced in time.
Third, the phenomenon of seesaw
The so-called see-saw phenomenon refers to the corrugated paperboard after being made. On the surface of the surface paper, there is a concave phenomenon between the back of the peak and the back of the peak, and the shape is the same as that of a domestic washboard. It is called a see-saw phenomenon.
The root cause of the seesaw phenomenon in corrugated board is mainly attributed to improper adhesive sizing, which is caused by the excess glue that collects on both sides of the peak. This situation is especially damaging for low-quantitative linerboards.
The specific methods of controlling the board seepage are: to adjust the amount of paper, and to use a higher amount of linerboard is the most direct and effective way to eliminate and reduce the board (but increase the cost); the use of high-quality adhesive can reduce The peak sizing amount; control the surface of the heating paper on the pre-heater, because the board paper is too dry, the glue intake is more, it is easy to produce the seesaw phenomenon; adjust the composite glue machine sizing roller and paper The degree of parallelism of the guide rollers and the gap between them, the degree of pressure of the guide roller (pressure roller) is strictly controlled to prevent the increase of the amount of glue after collapse.
Fourth, the cardboard water content control
In the process of production of corrugated board, the moisture content of the board is very important. When the moisture is too high, the processed board will appear soft, not quite, easy to collapse after the box. When the moisture content is low, the processed cardboard is hard, brittle, and easily burst after being packed. The control of board moisture is a complicated matter, which is mainly determined by the following two factors:
The moisture of the raw paper entering the factory must be strictly controlled. According to the current standard, the moisture of the original paper delivery state should be (8±2)%. It is better to set up a separate warehouse for storing the base paper, the temperature is generally (18 ± 3) °C, and the humidity is generally (35 ± 5)%. Do not put it in the open air, otherwise it is easy to cause moisture changes and the two ends are not the same as the middle.
Temperature is one of the decisive factors affecting the quality of corrugated board. It can not only adjust the moisture of the base paper, but also increase the temperature of the base paper, which is an important condition for curing the paste liquid. Therefore, a large number of preheaters and flat-plate dryers are installed in the cardboard production line to adjust the moisture content of the base paper and the single-sided paper, and the paste is finally cured to achieve the purpose of bonding.
In order to effectively control the moisture of finished corrugated board, we must pay attention to the following issues:
If the moisture in the paperboard is too high and the temperature of the preheating roll does not meet the requirements, the steam pressure of the boiler must be increased so that the steam supplied can reach saturated steam. In general, the steam pressure should be kept at 1.1 MPa ± 0.2 MPa.
If the water content is low, it is necessary to adjust the paper guide roller to reduce the preheating area. At the same time, the single-sided on-machine spray device (wet roller) should be fully utilized to spray the base paper to increase the moisture content of the base paper to meet the standard requirements.
When the flat-plate dryers are working, they cannot stop when they have no other last resort. One-sided machine should speed up before replacing the base paper, and accumulate more paper on the bridge; the composite machine should decelerate after receiving the signal, and wait until the single-faced machine completes the paper-receiving and then speed up. If the equipment must be stopped in case of a failure, the conveyor felt should be raised to prevent excessive moisture loss from the board dryer.
For single-sided machines, adjust the gap between the squeegee and the squeegee. Under normal circumstances, the gap between the rubber roller and the rubber roller is 0.2mm to 0.25mm. The gap between the rubber roller and the main corrugating roller in the thermal state should be 0.02mm larger than the thickness of the corrugated paper used. For the double-sided machine, the gap between the scraper roller and the top roller is also 0.2mm to 0.25mm. The gap between the roller and the top roller should be 0.05mm to 0.1mm smaller than the height of the single-faced corrugated board. And the gap between both ends of the roller should be consistent and can be measured with a feeler gauge.