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Prevention And Solving Measures Of Yellowing Of Coated White Paperboard
Oct 12, 2017

1 coated base paper process adjustment: the base paper of the pulp fiber all use bleached chemical pulp, and improve the amount of pulp, to strengthen the lining of the mechanical pulp coverage. The use of alkaline sizing process to reduce the amount of aluminum sulfate slurry to improve the base paper 13H value. Experiments show that the pH value of the base paper layer is between 6.5 and 8.0. In the process of making the paper, the drying temperature to be strictly controlled to ensure that the case of dry cardboard, try to reduce the drying temperature, and use the base paper and coated paper cold cylinder.

2 use better quality liquid brightener: Experiments show that the application of liquid brightener can reduce the degree of yellowing of coated products. It is to ensure that the product from the degree of self-improvement, the impact on the yellow was significantly lower than the powder whitening agent. Better quality liquid brightener must require a higher purity. Poor liquid whitening agent will not only cause unnecessary waste, but also easy to form the phenomenon of yellowing. Also in the paint formulations to use a good brightener, but also pay attention to the application of brightener carrier (auxiliary adhesive).

3 Appropriate use of color pigments: The use of color pigments is to maximize the whiteness (CIE), reduce the amount of fluorescent brightener, balance the different chemical raw materials to achieve the desired hue. In order to reduce the coated white paper back to yellow, the choice of color pigments not only requires easy operation, good affinity, but also have a higher lightfastness. So the best choice of high quality organic pigments, its various aspects of the performance is ideal. In the amount of color pigments should pay more attention, because too high or too low the amount of the purpose of not achieve the color. Too high, will exacerbate the extent of coating white paper back to yellow; too low, you can not achieve the appropriate whiteness.

4 to choose a reasonable ratio of coating adhesive: In the paint formula, in order to prevent and solve the phenomenon of coating white paper back to yellow, in the balance of formula costs and product performance requirements, the use of a single SBR latex as coating adhesive is almost impossible. Therefore, according to product performance requirements, you can choose styrene-butadiene latex and other latex mixed use, such as inexpensive styrene-acrylic latex, both to ensure the strength of coated white paper performance, but also reduce the degree of yellowing.

5 selection of new chemical additives: I cited the application of nano-silicon oxide oxide coating used in the study found that nano-silicon-based oxide because of its unique molecular structure, in reducing the coating yellow has a significant potential. In the eye aging test, the absolute value of the chromaticity b value decreases little. In addition, UV absorbers and antioxidants can also reduce the coating of white paper coated yellow.

6 Other factors that should be noted: for example, the pH of the coating, the purification of the coating water, the use of the coated starch, the moisture of the coated paperboard, the packaging and storage of coated paperboard, etc. Although these are not the main reasons for the formation of yellowing, but as long as the strengthening of all aspects of prevention, the application of white paper to yellow solution is also very effective.

In the process of solving the problem of coating the white paper back to the yellow, the coating base paper, fluorescent brightener, color pigments and adhesives are the main factors affecting the yellowing. Improve the raw materials production process conditions, the choice of high quality fluorescent brightener, color pigments, adjust the best amount; scientific to determine the best match with the adhesive, can effectively reduce the red paper coated white paper phenomenon.

The use of new chemical additives, such as nano-silicon oxide, UV absorbers and antioxidants and other chemical products will reduce the coated white paper back to the yellow phenomenon.

Strengthen the production of white paperboard control and packaging and storage conditions in all aspects of prevention, but also to solve the coated white paper back to the yellow favorable way.