The yellowing of all coated white cardboard in Gift Paper Boxes printing

The yellowing of all coated white cardboard in Gift Paper Boxes printing

Summary:

In most cases, the color boxes used in product packaging and the packaging boxes used in all kinds of commodity packaging are made of white cardboard. The newly purchased white cardboard is cut, printed, and processed into our product packaging boxes.

In most cases, the color boxes used in product packaging and the packaging boxes used in all kinds of commodity packaging are made of white cardboard. The newly purchased white cardboard is cut, printed, and processed into our product packaging boxes.

In today's day when material enjoyment is increasingly important and consumers' requirements for product quality and price, people have higher and higher requirements for the quality of packaging paperboard, (coated white paper is also called white cardboard) coated white paper is used as high-end packaging materials. , Its exquisite appearance quality has become the pursuit goal of people. However, the yellowing of the packaging box during use of the coated white paper seriously affects the appearance of the outer packaging material. The yellowing of coated white paper refers to the phenomenon that the whiteness of the product will decrease after a certain period of storage or exposure to sunlight. Research on the yellowing of coated white paper and its mechanism, find out the various factors of yellowing and the measures and methods to stabilize the whiteness, have attracted our attention. This article mainly combines production practice to analyze the yellowing phenomenon of coated white paper, and discuss how to prevent and solve the yellowing phenomenon.

　　 1. The formation mechanism of yellowing of coated white paper

　　 The latest research results show that the yellowing phenomenon is that the surface material of the paperboard reacts with oxygen in the air during the storage process and after exposure to sunlight, which changes the chemical structure of the surface material, thereby affecting the human visual effect. The degree of oxidation determines the severity of yellowing. The oxidation process is mainly due to the promotion of the following three factors: ① high temperature, ② ultraviolet light, ③ pH value.

　　 2. Factors affecting the yellowing of coated white paper

From the analysis of the promoting factors in the oxidation process and the material composition of the coated white paper, the main factors affecting the yellowing phenomenon of the coated white paper are as follows: coated white paper base paper, fluorescent whitening agent, coloring pigment, coating Cloth adhesives, etc.

　　3. Prevention and solution of yellowing of coated white paper

　　3.1. Process adjustment of coating base paper: The face pulp fibers of the base paper are all bleached chemical wood pulp, and the amount of face pulp is increased to strengthen the coverage of the mechanical pulp of the lining. The medium-alkaline sizing process is adopted to reduce the amount of aluminum sulfate in the flour paste and increase the 13H value of the base paper. Experiments have proved that the pH value of the base paper surface layer is between 6.5 and 8.0, and the effect is better. In the process of papermaking, the drying temperature should be strictly controlled. When the cardboard is dry, the drying temperature should be reduced as much as possible, and the cold cylinder of the base paper and the coated paper should be used well.

　　3.2. Choose liquid brighteners of better quality: Experiments have shown that the application of liquid brighteners can reduce the yellowing degree of coated products. While ensuring to improve the self-degree of the product, its effect on yellowing is significantly lower than that of powdery brighteners. Liquid brighteners of better quality must require higher purity. Liquid brighteners with poor purity will not only cause unnecessary waste, but also easily cause yellowing. In addition, fluorescent brighteners should be used well in coating formulations, and attention should be paid to the application of brightener carriers (auxiliary adhesives).

　　3.3. Reasonable application of tinting pigments: The use of tinting pigments is to maximize the whiteness (CIE), reduce the amount of fluorescent whitening agent, and balance different chemical raw materials to achieve the required hue. In order to reduce the yellowing of coated white paper, the selection of toning pigments requires not only easy operation, good affinity, but also high lightfastness. Therefore, it is best to choose high-quality organic pigments, and their performance in all aspects is ideal. Pay more attention to the amount of toning pigments, because too high or too low amounts will not achieve the purpose of toning. If it is too high, it will aggravate the yellowing of the coated white paper; if it is too low, it will not achieve the desired whiteness.

3.4. Choose a reasonable coating adhesive ratio: In the coating formulation, in order to prevent and solve the yellowing of the coated white paper, under the requirements of balancing the formulation cost and product performance, a single styrene butadiene latex is almost used as the coating adhesive. Is impossible. Therefore, according to product performance requirements, you can choose to mix styrene-butadiene latex with other latexes, such as cheap styrene-acrylic latex, which can not only ensure the strength performance of the coated white paper, but also reduce the degree of yellowing.

　　3.5. Use of new chemical additives: The author found that nano-silicon-based oxides are applied to coating formulations in the research, because of their unique molecular structure, nano-silicon-based oxides have obvious potential in reducing coating yellow. In the eye aging test, the absolute value of the chromaticity b value decreased very little. In addition, ultraviolet absorbers and antioxidants can also reduce the yellowing of the coated white paper coating.

　　3.6. Other factors that should be paid attention to: such as the pH value of the coating, the purification of the coating water, the use of coated starch, the moisture of the coated cardboard, the packaging and storage of the coated cardboard, etc. should be paid more attention. Although these are not the main causes of yellowing, as long as prevention is strengthened in all aspects, it is also very effective to solve the yellowing of coated white paper.

  4 Conclusion

　　4.1. In the production practice to solve the yellowing problem of coated white paper, the main factors affecting the yellowing are the coating of base paper, fluorescent brighteners, coloring pigments and adhesives. Improve the process conditions of base paper production, choose high-quality fluorescent whitening agents and coloring pigments, and adjust the optimal dosage; scientifically determine the best combination of adhesives, which can effectively reduce the yellowing of coated white paper.

　　4.2. The use of new chemical additives, such as nano-silicon-based oxides, ultraviolet absorbers and antioxidants and other chemical products will also reduce the yellowing of coated white paper.

　　4.3. Strengthening the production control of coated white paper and the prevention of packaging and storage conditions is also a favorable way to solve the yellowing of coated white paper.

　　All the involved processes are controlled, the work is standardized and the process is standardized, so our coated white cardboard is also of first-class quality. Of course, the packaging boxes and color boxes produced are also first-class. These are shy and everyone works hard together.

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