[Chinese Packaging Network News] friends engaged in the carton industry, every year for some time to be chased by the customer to chase the butt asked the same sentence: Why is it so soft! This problem is really troublesome and difficult to solve, because the fiber used in carton base paper is a kind of hydrophilic material and it is naturally hygroscopic. In wet weather such as the rainy season, when the relative humidity in the air is too high, the cartons are in direct contact with the air and will absorb the water in the air, resulting in the production of corrugated cartons. The entire cardboard is also soft. The face of evasive complaints, or even returns, fines, and compensation, etc., to solve the cardboard softening has become a top priority for the carton factory.
First, the moisture resistance of paper and board
Raw paper and corrugated paper, especially corrugated paper, are highly absorbent;
The long exposure time of paper in moist air, the increase of water price, the paper's lateral crushing strength will be significantly reduced. When the relative humidity is 85%, the ring crush strength will drop by 60%.
Solution
It is recommended to use a base paper with a better waterproof and dampproof effect, especially pitting. To test the waterproof effect of the base paper, the surface water absorbency of the base paper can be tested by Ke Boyi. When the surface water absorbency is below 50 g/m2 (60S), the waterproof and moisture proof effect is better. If you can not test the instrument, directly on the cardboard or corrugated paper sprinkle a few drops of water, wait 60 seconds after the paper dry, observe whether the surface of the paper after the infiltration of discoloration, if not, to prove waterproof and dampproof effect is better.
In order to improve the surface water resistance of paper, paper mills usually need to increase the proportion of waterproof auxiliaries in the surface sizing starch paste in the papermaking process. Because the auxiliaries are expensive, the water-repellent base paper has a lower water resistance than the base paper. To be higher than 50-100 yuan, the higher the lower the gram weight, the higher. Therefore, the carton factory needs to actively communicate with the customers of the carton and appropriately increase the price.
Second, corrugated board production process
The main means to solve the softening of the carton is to select a good material, followed by the production process. The factor that softens the carton is to absorb excess water. Therefore, during the carton production and processing, the moisture in the carton should be removed as much as possible.
Solution:
The base paper warehouse is isolated from the outside as much as possible, absolutely avoiding the damp air from wandering freely inside the warehouse. When appropriate, install a dehumidifier in the warehouse to ensure that the relative humidity is below 65%.
When the base paper is in the warehouse, it will absorb the moisture in the moist air. When the machine is on, it should increase the preheating angle of the base paper on the dryer. If the effect is still not good, it can slow down the speed and increase the steam pressure.
Increase the powder content when making the paste, reduce the amount of glue, can reduce the moisture of the carton. Increasing the borax ratio also improves the feel of the corrugated board.
Reducing the amount of board stacking on the overpasses and slowing down the speed, especially after the stacking of corrugated board is fully dehumidified.
Third, the storage environment:
The cardboard after going offline shall be used to remove the vapors that have not been scattered to avoid the formation of condensed water due to temperature difference. The environment for storing cardboard or carton shall be kept ventilated and ventilated. The cardboard cartons shall not be directly placed on the ground, and the pallets (pallets, splints) shall be used. . Pay attention to the space between each other during storage to facilitate ventilation and heat dissipation.
It is recommended to use wood pallets, which can absorb the moisture on the ground, and the size is suitable for cardboard cartons. It is also safe to keep the storage environment ventilated and ventilated, and use the wrapping film for external protection, which can effectively reduce and isolate the phenomenon of weather softening.
Now many manufacturers have started to use dehumidifiers, and if they can ensure that the relative temperature of the warehouse is below 65%, the hardness of the cardboard will increase significantly.
