Causes and Treatments of Yellowing of White Cardboard Cases

[Chinese Packaging Network News] All kinds of packaging used for packaging of goods, in most cases are made of white cardboard. The newly purchased white paperboard, which has undergone slitting, printing, and subsequent processing and processing, has become our product packaging box. Based on the production practice, this article analyzes the phenomenon of yellowing of coated whiteboard papers and discusses how to prevent and solve the phenomenon of yellowing.

With the increasing emphasis on material enjoyment, people are increasingly demanding quality packaging cardboard. Coating white paper as high-grade packaging materials, its exquisite appearance quality has also become people's pursuit of goals. However, the yellowing phenomenon of the packaging box during the use of the coated whiteboard paper has seriously affected the appearance of the packaging material. Based on the production practice, this article analyzes the phenomenon of yellowing of coated whiteboard papers and discusses how to prevent and solve the phenomenon of yellowing.

1. The yellowing phenomenon of coating whiteboard paper

The latest research results show that the phenomenon of yellowing is that the cardboard surface material reacts with oxygen in the air during storage and after exposure to sunlight, which changes the chemical structure of the surface materials and thus affects the visual effects of humans. The degree of oxidation determines the severity of yellowing. The oxidation process is mainly due to the following three factors: 1 high temperature, 2 UV, 3 pH.

2. Factors that affect the yellowing of coated whiteboard

From the promotion factors in the oxidation process and the analysis of the material composition of the coated whiteboard paper, the factors affecting the yellowing of the coated whiteboard paper mainly include the following aspects: coated white paper base paper, fluorescent whitening agent, color pigment, and coating Cloth adhesive and so on.

3. Prevention and remedy of the phenomenon of yellowing in coated whiteboard

Adjustment of the process of coating the base paper: The bleached chemical pulp of the base paper is used for bleaching, and the amount of batter is increased to increase the coverage of the lining mechanical pulp. The use of alkaline sizing process,

Reduce the amount of aluminum sulfate in the batter and increase the 13H value of the base paper. It has been proved by experiments that the pH value of the paper surface layer is better between 6.5 and 8.0. In the process of papermaking, the temperature of the drying should be strictly controlled to ensure that the board is dry, the drying temperature should be reduced as much as possible, and the cold paper of the base paper and coated paper should be used.

Use better quality liquid brighteners: It has been experimentally proven that the use of liquid brighteners can reduce the degree of yellowing of coated products. It ensures that the self-degree of the product is increased while the yellowing effect is significantly lower than the powdery whitening agent. Better quality liquid brighteners must require higher purity. Less pure liquid brighteners not only cause unnecessary waste, but also tend to cause yellowing. In addition to the use of fluorescent whitening agents in coating formulations, attention should also be given to the use of brightener carriers (adhesives).

Reasonable application of color pigments: The use of color pigments is to maximize whiteness (CIE), reduce the amount of fluorescent brighteners, and balance different chemical raw materials to achieve the desired hue. In order to reduce the yellowing of coated whiteboards, the use of tinting pigments requires not only easy operation but also high lightfastness. Therefore, it is best to use high quality organic pigments, and its performance in various aspects is ideal. More attention should be paid to the amount of hueing pigments, which will exacerbate the degree of yellowing of the coated white paper; if it is too low, the desired whiteness will not be achieved.

Choosing a reasonable proportion of coating adhesive: In order to prevent and solve the phenomenon of yellowing of coated white paper in the coating formulation, it is almost impossible to use a single styrene-butadiene latex as a coating adhesive under the requirements of balanced formulation cost and product performance. possible. Therefore, according to product performance requirements, you can choose styrene butadiene latex and other latex mixed use, such as low-cost styrene-acrylic latex, both to ensure the strength of coated white paper, but also reduce the degree of yellowing.

Selection of new chemical additives: In the study of nano-silicon oxides used in coating formulations, the authors found that nano-silicon oxides have a clear tendency to reduce coating yellow due to their unique molecular structure. In the aging test, the absolute value of the color b value decreases very little. In addition, UV absorbers and antioxidants can also reduce the yellowing of coated white paper coatings.

Other factors that should be taken care of: such as the pH value of the coating, the purification of coating water, the use of coated starch, the moisture of the coated paperboard, the packaging and storage of coated cardboard, etc. should be strengthened. Although these are not the main reasons for the formation of yellowing, as long as prevention is strengthened in all aspects, the yellowing of coated whiteboard paper is also effective.