People is higher and higher requirements about the quality of the packaging board, coated white board paper as high-grade packaging materials, its elegant appearance quality has become people's pursuit of goals.But the coated white board paper yellowing phenomenon has seriously affected the outer packing material is beautiful.Coated white board paper yellowing refers to products stored after a certain time, or after sunlight, the white will have to fall.The coated white board paper yellowing phenomenon and the mechanism of yellowing of the various factors and measures and methods to stabilize the whiteness, has been increasingly cause the attention of us.Long printing group in combination with production practice, analysis of coated white board paper yellowing phenomenon, how to prevent and solve the paper yellowing phenomenon.
1. The formation mechanism of coated white board paper yellowing phenomenon
The latest research results show that the yellowing phenomenon is cardboard in storage during and after sun exposure, cardboard surface materials react with oxygen in the air, to change the chemical structure of the surface material, which affect the person's visual effect.The severity of the oxidation degree determines the yellowing.Oxidation process is mainly due to the following three factors of: (1) high temperature, (2) ultraviolet light, (3) the pH.
2. The influencing factors of coated white board paper yellowing phenomenon
From promoting factors in the process of oxidation and coated white board paper material composition analysis, the influencing factors of coated white board paper yellowing phenomenon main has the following several aspects: coated white board base paper, fluorescent whitening agent, color paint, coating, adhesive, etc.
3. The coated white board paper yellowing phenomenon of prevention and solution measures
(1) coating base paper process adjustment: base paper MianJiang fiber all adopt the bleached chemical pulp, and increase the dosage of the MianJiang, strengthen transform mechanical pulp layer of coverage.Use of alkaline sizing technology, reducing MianJiang the amount of aluminium sulfate, increase the PH value of the base paper.Proved by the experiment, base paper surface of the pH value between 6.5 ~ 8.0 effect is better.In the process of manufacturing, to strictly control the temperature of drying, ensure the cardboard under the condition of dry, try to reduce the drying temperature, and the cold cylinder with good base paper and coated paper.
(2) to choose a good quality liquid whitener: proved by the experiment, the application of liquid whitener can reduce the yellowing degree of coating products.It at the same time the degree of assurance to improve product, the effect on the yellowing significantly lower than the powdered whitening agent.Quality good liquid brightener require high purity.Low purity of liquid whitening agent will not only cause unnecessary waste, and easy to form the yellowing phenomenon.In addition to good use fluorescent whitening agent in the coating formula, but also pay attention to the application of carrier brightener.
(3) the reasonable application of color pigments, the use of color pigments, is to try to improve the whiteness (CIE), reducing the amount of fluorescent whitening agent, the balance of different chemical raw materials in order to achieve the required color.In order to reduce the coated white board paper yellowing, choose color pigments requires not only easy to operate, good affinity, but also had a higher degree of fast.So it's best to choose high quality organic pigments, the performance of its various aspects is ideal.More attention should be paid on the amount of color pigments, because of too high or too low dosage reach the purpose of the palette.Too high, will increase the extent of the coated white board paper yellowing;Too low, can not reach the required appropriate whiteness.
(4) to choose a reasonable proportion of coating adhesive: in the paint recipe, in order to prevent and solve the coated white board paper yellowing phenomenon, at the request of the balance formula cost and product performance, using a single butyl benzene latex as coating binder is almost impossible.So according to the product performance requirements, can choose butyl benzene latex and other latex mixed use, such as the low price of styrene acrylic latex, which can ensure the strength of the coated white board paper performance, and can reduce the yellowing degree.
(5) should be paid attention to other factors, such as pH coating, coating with water purification, coating the use of starch and water of coated paperboard, coated cardboard packaging and storage and so on all must strengthen the attention.Although these are not the main reason for the yellow formation, but as long as prevention has been stepped up in various aspects, to the solution of the coated white board paper yellowing is very effective.
In the production practice to solve the problem of coated white board paper yellowing process, coating base paper, fluorescent whitening agent, color pigments and adhesive are the main factors influencing the yellowing.Improve base paper production process conditions, choose high quality fluorescent whitening agent, color pigments, adjust the best dosage;Science and determine the optimal collocation of adhesive, can effectively reduce the coated white board paper yellowing phenomenon.
China Book Printing
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