People have higher and higher requirements for the quality of packaging paperboard, card game printing wholesale as high-end packaging materials, its exquisite appearance quality has become the pursuit of people's goals. However, the yellowing phenomenon of card game printing wholesale has seriously affected the appearance of the outer packaging materials. card game printing wholesale yellowing refers to the phenomenon that the whiteness of the product will decrease after a certain period of storage or exposure to sunlight. To study the yellowing phenomenon of card game printing wholesale and its mechanism, to find out the various factors of yellowing and the measures and methods to stabilize whiteness have attracted our attention increasingly. This paper mainly combined with the production practice of our company, the card game printing wholesale yellowing phenomenon is analyzed, how to prevent and solve the yellowing phenomenon is discussed.

1.card game printing wholesale yellowing formation mechanism

The latest research results show that the yellowing phenomenon is that the cardboard surface material reacts with oxygen in the air during storage and after sunlight irradiation, changing 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 card game printing wholesale yellowing phenomenon

From the analysis of the promoting factors in the oxidation process and the material composition of card game printing wholesale, the main factors affecting the yellowing phenomenon of card game printing wholesale are as follows: card game printing wholesale base paper, fluorescent whitening agent, toning pigment, coating adhesive, etc.

2.1 Coating base paper

2.1.1 Fiber type and composition of base paper: mainly the composition of surface layer fiber. The base paper pulp of card game printing wholesale is generally composed of bleached chemical wood pulp, so the yellowing of the base paper is mainly due to heat induction. The yellowing of mechanical pulp is mainly light induced yellowing, so it is more serious than chemical pulp yellowing during storage.

2.1.2 pH value of base paper: acidic board is more likely to cause yellowing than medium alkaline board.

2.1.3 Other raw materials of base paper: such as filler materials, retention agents and other raw materials also have a little impact.

2.2 Fluorescent whitening agent

Fluorescent whitening agent is mainly a derivative of stilbene disulfonic acid (or tetrasulfonic acid), because the lignin remaining in the pulp or some pigment components in the paint will cause the yellowing of the cardboard, and the use of fluorescent whitening agent is to eliminate the yellowish tone, is the appearance of improving the quality of the cardboard. Although the effect of the whitening agent is short-lived, because it is yellow, more amounts of the whitening agent will also affect the yellowing of the cardboard.

2.3 Color pigments

2.3.1 Different types of colorants are often used as palette pigments for card game printing wholesale coatings, and the requirements for them must be sun fast. Direct dyes and alkaline dyes are cheaper, but have lower fastness to light.

2.3.2 The amount of color pigments used will aggravate the yellowing degree of coated white plate paper.

2.4 Apply adhesive

There are usually three kinds of adhesives used for card game printing wholesale: acetate latex, styrene-acrylic latex, and styrene-butadiene latex. Acetate latex has the least effect on yellowing, and styrene butadiene latex has the greatest effect on yellowing because of its special chemical structure.

2.5 Comparison of the effects of fiber types and adhesives on the yellowing of card game printing wholesale

3.card game printing wholesale yellowing phenomenon prevention and solution measures

3.1 Process adjustment of coating base paper: the 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 on the lining layer. The medium alkaline sizing process was used to reduce the amount of aluminum sulfate in the pulp and increase the 13H value of the base paper. Experiments have proved that the pH value of the base paper surface is between 6.5 and 8.0. In the process of manufacturing, the drying temperature should be strictly controlled, to ensure that the cardboard is dry, as far as possible to reduce the drying temperature, and use the base paper and coated paper cold tank.

3.2 Selection of good quality liquid whitening agent: experiments have proved that the application of liquid whitening agent can reduce the degree of yellowing of coated products. While ensuring the improvement of product self-degree, its effect on yellowing is obviously lower than that of powder whitening agent. Good quality liquid whitening agent must require high purity. The liquid whitening agent with poor purity will not only cause unnecessary waste, but also easily form the phenomenon of yellowing. In addition, fluorescent whitening agents should be used in the coating formulation, and attention should be paid to the application of whitening agent carriers (auxiliary adhesives).

3.3 Reasonable application of toning pigments: The use of toning pigments is to maximize the whiteness (CIE), reduce the amount of fluorescent whitening agents, and balance different chemical raw materials to achieve the required hue. In order to reduce the yellowing of card game printing wholesale, the selection of color pigments requires not only easy operation, good affinity, but also high light fastness. Therefore, it is best to choose high-quality organic pigments, and 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 the amount can not achieve the purpose of color. Too high, will aggravate the degree of yellow card game printing wholesale; Too low, it will not achieve the required appropriate whiteness.

3.4 Select a reasonable coating adhesive ratio: In the coating formula, in order to prevent and solve the phenomenon of card game printing wholesale yellow, under the requirements of balancing the formula cost and product performance, it is almost impossible to use a single styrene butadiene latex as a coating adhesive. Therefore, according to the performance requirements of the product, you can choose to mix styrene butadiene latex and other latex, such as cheap styrene acrylic latex, which can ensure the strength of the card game printing wholesale and reduce the degree of yellowing.

3.5 Selection of new chemical auxiliaries: In the study of nano-silicon based oxides applied to coating formulations, the author found that nano-silicon based oxides have a significant potential to reduce the yellow coating because of their unique molecular structure. In the eye aging test, the absolute value of chroma b decreases very little. In addition, UV absorbers and antioxidants can reduce the yellowing of the card game printing wholesale coating.

3.6 Other factors that should be paid attention to: such as the pH value of the paint, the purification of the paint water, the use of coated starch, the moisture of coated cardboard, and the packaging and storage of coated cardboard should be paid more attention. Although these are not the main reasons for the formation of yellowing, as long as prevention is strengthened in all aspects, the solution to card game printing wholesale yellowing is also very effective.

4. Conclusion

4. In the production practice of solving the yellowing problem of card game printing wholesale, coating base paper, fluorescent whitening agent, toning pigment and adhesive are the main factors affecting yellowing. Improve the process conditions of base paper production, select high quality fluorescent whitening agent, color pigment, adjust the best dosage; Scientific determination of the best combination of adhesives can effectively reduce the yellowing phenomenon of card game printing wholesale.

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