Small Paper Jewelry Boxes in the printing of all coated white card paper yellowing remove yellow tips

Small Paper Jewelry Boxes in the printing of all coated white card paper yellowing remove yellow tips

Color Boxes used in the packaging of Small Paper Jewelry Boxes and boxes used in the packaging of various commodities are mostly made of white card paper. The newly purchased white card paper, into over-cutting, printing, and after processing becomes our product packaging box.

Today, with the increasing emphasis on material enjoyment and consumers' requirements on product quality and price, people have higher and higher requirements on the quality of packaging board. (coated white board paper, also known as white board paper) coated white board paper, as a high-grade packaging material, has become people's pursuit of exquisite appearance quality. However, the yellowing of the packaging box during the use of coated whiteboard seriously affects the appearance of the outer packaging materials. Coated whiteboard yellowing refers to the product after a certain time of storage, or by sunlight, the whiteness will have a certain decline. It has been paid more and more attention to study the yellowing phenomenon of coated whiteboard paper and its mechanism, find out the various factors of yellowing and the measures and methods to stabilize the whiteness. Based on the production practice, this paper analyzes the yellowing phenomenon of coated whiteboard paper and discusses how to prevent and solve the yellowing phenomenon.

1. Formation mechanism of yellowing on coated whiteboard paper

The latest research results show that the yellowing phenomenon is caused by the reaction between the surface material of cardboard and oxygen in the air during storage and after sunlight irradiation, which changes the chemical structure of the surface material, thus affecting the visual effect of people. 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, ③pH value.

2. Factors affecting the yellowing of coated whiteboard paper

From the promoting factors in the oxidation process and the analysis of the material composition of coated white board paper, the factors that affect the yellow phenomenon of coated white board paper mainly include the following aspects: coated white board base paper, fluorescent whitening agent, color pigment, coated adhesive, etc.

3. Prevention and solution of yellow coated whiteboard paper

3.1 Process adjustment of coating base paper: the flour pulp fibers of base paper are all bleached chemical wood pulp, and the amount of flour pulp is increased to strengthen the coverage of mechanical pulp of lining layer. The medium alkaline sizing process was used to reduce the amount of aluminum sulfate in flour paste and increase the 13H value of base paper. The experimental results show that the pH value of base paper surface layer is between 6.5 and 8.0. In the process of manufacturing, the drying temperature should be strictly controlled, and the drying temperature should be reduced as far as possible to ensure that the cardboard is dry, and the cold cylinder of base paper and coated paper should be used well.

3.2. Select liquid whitener with better quality: it has been proved by experiments that the application of liquid whitener can reduce the yellowing degree of coated products. The effect of it on yellowing is obviously lower than that of powder whitening agent. A better quality liquid whitening agent must require higher purity. Poor purity of the liquid whitening agent will not only cause unnecessary waste, and easy to form the phenomenon of yellowing. In addition, in the formulation of coatings to use good fluorescent whitening agent, but also pay attention to the application of whitening agent carrier (auxiliary adhesive).

3.3 Rational application of toning pigments: The use of toning pigments is to improve the whiteness (CIE) as much as possible, reduce the amount of fluorescent whitening agent, and balance different chemical raw materials to achieve the desired hue. In order to reduce the yellowness of coated whiteboard paper, the selection of toning pigments not only requires easy operation, good affinity, but also has a high degree of fastness. Therefore, the best choice of high quality organic pigments, its performance in all aspects is more ideal. More attention should be paid to the amount of color pigments, because too high or too low amount can not achieve the purpose of color. If it is too high, it will aggravate the degree of yellow coated whiteboard; If it is too low, the desired whiteness will not be achieved.

3.4. Select a reasonable proportion of coating adhesive: In the coating formulation, in order to prevent and solve the yellowing phenomenon of coated whiteboard paper, it is almost impossible to use a single styrene butadiene latex as coating adhesive under the requirement of balancing formula cost and product performance. Therefore, according to the product performance requirements, you can choose styrene butadiene latex and other latex mixed use, such as cheap styrene acrylate latex, not only can ensure the strength of coated white paper performance, but also can reduce its yellowing degree.

3.5 Selection of new chemical auxiliaries: The author found that nano-silicon-based oxides have obvious potential in reducing coating yellow due to their unique molecular structure in the study of the application of nano-silicon-based oxides in coating formulation. In the eye aging test, the absolute value of chrominance b decreased very little. In addition, UV absorbers and antioxidants can also reduce the yellow coating of coated white paper.

3.6. Other factors that should be paid attention to: for example, the pH value of the coating, the purification of the coating water, the use of coated starch, the moisture of coated board, and the packaging and storage of coated board should be paid more attention. Although these are not the main reason for the formation of yellowing, but as long as the prevention is strengthened in all aspects, the solution to coated whiteboard yellowing is also very effective.

4. Conclusion

4.l. In the production practice process of solving the yellowing problem of coated white board paper, the main factors affecting yellowing are coated base paper, fluorescent whitening agent, toning pigment and adhesive. Improve the production process conditions of base paper, choose high-quality fluorescent whitening agent, toning pigment, adjust the optimal dosage; Scientific determination of the best match of adhesive can effectively reduce the yellow phenomenon of coated whiteboard paper.

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

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