In the industry, corrugated paper is often used in the design of cardboard boxes, and how to choose the hardness of corrugated paper? Today I am going to tell you about it.

    This problem is really troublesome and difficult to solve, because the fiber used in the base paper of cardboard boxes is a hydrophilic substance, which is naturally absorbent. In humid weather such as the rainy season, when the relative humidity in the air is too high, the cardboard boxes are in direct contact with the air, which will absorb the moisture in the air, resulting in the production of corrugated cardboard boxes, and the whole cardboard box is also soft. In the face of unavoidable complaint calls, even returns, fines, compensation, etc., solving the softening of cardboard has become the top priority of the cardboard boxes factory.

  Below, I will provides you with a package of solutions to solve the softening of cardboard boxes.

1. Moisture resistance of paper and cardboard

Base paper and corrugated paper, especially corrugated paper, have strong water absorption; when the paper is exposed to humid air for a long time, the water price increases, and 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%.

Solution: It is recommended to use base paper with good waterproof and moisture-proof effect, especially the corrugated paper with pits. To test the waterproof effect of the base paper, the surface water absorption of the base paper can be tested by the Kebo instrument. Generally, when the surface water absorption is below 50 g/square meter (60S), the waterproof and moisture-proof effect is better. If you fail to test the instrument, sprinkle a few drops of water directly on the boxboard or corrugated paper, wait for 60 seconds to dry with paper, and observe whether there is discoloration after penetration on the surface of the paper. If not, it proves that the waterproof and moisture-proof effect is good.

Usually, in order to improve the water repellency of the base paper surface, the paper mill needs to increase the proportion of the water repellent additive in the surface sizing starch paste in the papermaking process. Since the additive is expensive, the cost per ton of the base paper with good water repellency is higher than that of the base paper with poor water repellency. To be higher than 50-100 yuan, the lower the weight, the higher the cost. Therefore, the cardboard box factory needs to actively communicate with the cardboard box customers and appropriately increase the quotation.

2. Corrugated cardboard production process

The main method to solve the softening of cardboard boxes is to choose the material, and the second depends on the production process. The softening factor of the cardboard boxes is the absorption of excess water. Therefore, during the production and processing of the cardboard boxes, the water in the cardboard boxes should be removed as much as possible.

Solution: The base paper warehouse should be isolated from the outdoors as much as possible to avoid damp air wandering freely inside the warehouse. When appropriate, install a dehumidifier in the warehouse to ensure that the relative temperature is below 65%.

When the base paper is in the warehouse, it will absorb the moisture in the humid air. The preheating angle of the base paper on the drying cylinder should be increased when the machine is installed. If the effect is still not good, the speed of the vehicle can be slowed down and the steam pressure can be increased.

When making paste, increase the content of powder and reduce the amount of glue, which can reduce the water content of cardboard boxes. In addition, increasing the proportion of borax will also improve the feel of corrugated cardboard.

Reduce the amount of cardboard stacking over the paper flyover, slow down the speed of the vehicle, especially dehumidify the corrugated cardboard after stacking

3. Storage environment

After the cardboard is offline, the steam that has not been dissipated should be pumped out to avoid condensation caused by temperature difference. The environment for storing cardboard or cardboard boxes should be ventilated and ventilated. Cardboard boxes should not be placed directly on the ground. bear. During storage, pay attention to the gap between them to facilitate ventilation and heat dissipation.

Solution: It is recommended to use a wooden backing board, which can absorb the moisture on the ground, and the size is suitable for the cardboard boxes; keep the storage environment ventilated and ventilated, and use the wrapping film for external protection, which can effectively reduce and isolate the weather-induced softening phenomenon.

Now many manufacturers have begun to use dehumidifiers. If the relative temperature of the warehouse can be ensured below 65%, the hardness of the cardboard will be significantly improved.

4. Transportation environment

During the delivery of cardboard boxes, some use open-top trucks for transportation, and some use vans. Usually the latter can protect the drying of the cardboard more than the former, avoiding and reducing softening.

Solution: It is recommended to use a van for transportation, which is also commonly used by major supply companies at present.

5. Processing technology of cardboard boxes

The corrugated cardboard should enter the next process as soon as possible after it comes off the cardboard assembly line. The longer the cycle, the easier the cardboard will absorb the moisture in the air and soften.

In addition, when printing, especially multi-color printing or large solid printing, the cardboard boxes are easily compressed due to the pressure of the printing plate.

Solution: Minimize the residence time of cardboard boxes during production and processing, and avoid softening after being exposed to humid air for too long. The workshop should also be moderately isolated from the outdoors to avoid direct blowing of water vapor into the workshop.

 Cardboard boxes try to ensure the hardness of the corrugated cardboard before printing, and avoid excessive pressure during printing. The die-cutting process should try to avoid using the circular die-cutting process that does great harm to the flat pressing of the cardboard.