Friends engaged in the carton industry, for a period of time every year, the customer procurement lady chased the buttocks and asked the same sentence: Why is it so soft!
This problem is really troublesome and difficult to solve, because the fiber used in the carton base paper is a hydrophilic substance that is naturally absorbent. In humid weather such as the rainy season, when the relative humidity in the air is too high, the carton will be in direct contact with the air, which will absorb the moisture in the air, resulting in the corrugated carton produced, and the entire cardboard is also soft. In the face of evasive complaints, even returns, fines, compensation, etc., solving cardboard softening has become the top priority of the carton factory.
Below, the editor will provide you with a package solution to solve the softening of cartons.
1. Moisture resistance of paper and cardboard
Base paper and corrugated paper, especially corrugated paper, have strong water absorption; if the paper is exposed to moist air for a long time, the water price increases, the transverse ring compressive strength of the paper will decrease significantly. When the relative humidity is 85%, the ring compressive strength It will drop by 60%.
It is recommended to switch to base paper with better waterproof and moisture-proof effect, especially tile paper with pits. To check the waterproof effect of the base paper, the surface water absorption of the base paper can be tested by the Kobo meter. Generally, when the surface water absorption is below 50 grams/square meter (60S), the waterproof and moisture-proof effect is better. If you fail to test the instrument, sprinkle a few drops of water on the cardboard or corrugated paper, wait for 60 seconds, and then absorb it with the paper. Observe whether the paper surface has discoloration after penetration. If not, it proves that the waterproof and moisture-proof effect is better.
Generally, in order to improve the water resistance of the base paper surface, paper mills need to increase the proportion of water repellent additives in the surface sizing starch paste in the papermaking process. Because the additives are expensive, base paper with good water resistance costs per ton compared to base paper with poor water resistance. It should be 50-100 yuan higher, and the lower the weight, the higher the cost. Therefore, the carton factory needs to actively communicate with the carton customers and increase the quotation appropriately.
2. Corrugated cardboard production process
The main method to solve the softening of cartons is to choose the material, and then it depends on the production process. The reason for the softening of the carton is the absorption of excess water. Therefore, during the production and processing of the carton, the water in the carton should be removed as much as possible.
The raw paper warehouse is isolated from the outdoors as much as possible, and absolutely avoid moist air wandering freely inside the warehouse. When appropriate, install a dehumidifier in the warehouse to ensure that the relative temperature is below 65%.
The base paper will absorb moisture in the moist air when it is in the warehouse. The preheating wrap angle of the base paper on the dryer should be increased when the machine is used. If the effect is still not good, you can slow down the speed and increase the steam pressure.
When making paste, increase the content of powder and reduce the amount of glue, which can reduce the moisture of the carton. In addition, increasing the proportion of borax will also improve the feel of corrugated cardboard.
Reduce the amount of cardboard that crosses the paper flyover and slow down the speed, especially after corrugated cardboard is stacked to fully dehumidify.
3. Storage environment
After the cardboard is offline, the steam that has not been dissipated should be evacuated to avoid condensation caused by temperature differences. The environment for storing cardboard or cartons should be ventilated. Cardboard cartons should not be placed directly on the ground. Use pads (pallets, plywood) to support them. . Pay attention to the gap between each other during storage to facilitate ventilation and heat dissipation.
It is recommended to use a wooden backing board, which can absorb part of the moisture on the ground, and the size is suitable for the cardboard box; keep the storage environment ventilated and breathable, and use stretch film for external protection, which can effectively reduce and isolate the softening phenomenon caused by the weather.
Many manufacturers now start to use dehumidifiers. If the relative temperature of the warehouse is below 65%, the hardness of the cardboard will be significantly improved.
4. Transportation environment
In the product delivery process, some use open trucks and some use vans. Usually the latter is better than the former to protect the dryness of the cardboard and cardboard, avoiding and reducing softening.
It is recommended to use vans for transportation, which are also commonly used by major supplier companies.
5. Carton processing technology
Corrugated cardboard should enter the next process as soon as possible after it is off the cardboard assembly line. The longer the cycle, the cardboard will easily absorb the moisture in the air and soften.
In addition, when printing, especially multi-color printing or large-scale solid printing, the paper box is likely to be softened due to the pressure of the printing plate.
Try to shorten the residence time of the carton in the production and processing process, and avoid being exposed to moist air for too long and softening. The workshop should also be properly isolated from the outdoors to avoid direct blowing of water vapor into the workshop.
Try to ensure the hardness of the corrugated board before printing, and avoid excessive pressure when printing. The die-cutting process should try to avoid the use of the circular die-cutting process, which is very harmful to the flat press of the cardboard.
In short, the problem of carton softening, in the final analysis, is the moisture problem. Only by doing everything possible to prevent the carton from absorbing water during the storage of raw paper, corrugated board processing, carton processing, storage and transportation, can we be hardened.