[Chinese Packaging Network News] Friends working in the corrugated box industry often face a recurring issue from customers: "Why is the box so soft?" This problem is frustrating and challenging to solve, as the base paper used in corrugated cardboard is hygroscopic by nature. In humid weather, such as during the rainy season, when the air's relative humidity is high, the boxes absorb moisture from the air, causing the entire cardboard structure to become weak and soft. This can lead to customer complaints, returns, fines, or even compensation. As a result, preventing cardboard softening has become a top priority for corrugated box manufacturers.
First, the moisture resistance of paper and board
The raw paper and corrugated paper, especially the corrugating medium, are highly absorbent. Prolonged exposure to moist air increases the water content, which significantly reduces the lateral crushing strength. At 85% relative humidity, the ring crush strength can drop by as much as 60%.
Solution
It is recommended to use base paper with better waterproof and moisture-resistant properties, especially for corrugated boards. To test the waterproof effect of the base paper, you can measure its surface water absorption using a KES-FB1 device. If the surface water absorption is below 50 g/m² (60 seconds), it indicates good water resistance. If you don't have testing equipment, simply sprinkle a few drops of water on the cardboard or corrugated paper, wait 60 seconds, and check if the paper surface changes color after drying. If there is no discoloration, it means the paper has good waterproofing properties.
To improve the water resistance of the paper, paper mills usually increase the amount of waterproofing agents in the surface sizing starch solution. However, these agents are expensive, and water-repellent base papers tend to be more costly, ranging from 50 to 100 yuan higher than regular paper. The lower the grammage, the higher the cost. Therefore, corrugated box manufacturers should communicate with their customers and consider adjusting prices accordingly.
Second, the production process of corrugated boards
The main way to address the softening issue is to choose high-quality materials, followed by optimizing the production process. Since moisture absorption is the main cause of softening, it’s crucial to remove as much moisture as possible during production.
Solution:
Keep the base paper warehouse isolated from external moisture, avoiding any damp air from entering. Installing a dehumidifier in the warehouse is recommended to maintain a relative humidity below 65%.
When the base paper is stored, it absorbs moisture from the air. When the machine is running, increase the preheating angle of the base paper on the dryer. If the results are still unsatisfactory, reduce the speed and increase the steam pressure.
Increasing the powder content in the paste and reducing the glue amount can help lower the moisture level in the corrugated board. Also, increasing the borax ratio improves the feel and quality of the board.
Reduce the number of stacked boards on the conveyors and slow down the speed, especially after the corrugated boards are fully dried.
Third, storage environment
After the cardboard comes off the line, ensure that any remaining moisture is removed to prevent condensation caused by temperature differences. The storage area for cardboard or boxes should remain well-ventilated. Never place cardboard directly on the ground; instead, use pallets or skids. Maintain proper spacing between stacks to allow for air circulation and heat dissipation.
It is recommended to use wooden pallets, which can absorb moisture from the floor. Choose pallets that are appropriately sized for the cardboard boxes. Keeping the storage area ventilated and using wrapping film for external protection can effectively reduce and prevent weather-related softening.
Many manufacturers now use dehumidifiers, and if the warehouse’s relative humidity can be kept below 65%, the hardness of the cardboard will improve significantly.
Electric Hair Clipper,Usb Charging Barber Tools,Cordless Electric Hair Clipper,Usb Charge Hair Clipper
ZHEJIANG SHENGFA ELECTRIC APPLIAMNCES CO.,LTD , https://www.sfelectricappliances.com