Water-based ink is referred to as ink, and flexible water-based ink is also known as liquid ink, which is mainly made of water-soluble resins, organic pigments, solvents and related additives by composite grinding processing. Water-based ink is especially suitable for tobacco, wine, food, beverages, medicines, children's toys and other packaging and printing products with strict sanitary conditions.
 
01 the basic formula of water-based ink:
·Water-soluble acrylic resin 25% ~ 35%
·Water 15% ~ 25%
·Ethanol 5% ~ 15%
·Triethylamine 5% ~ 10%
·Paint 10% ~ 30%
·Additives 1% ~ 3%
 
02 the composition of water-based ink
Water-based ink is composed of water-based polymer emulsion, pigment, surfactant, water and other additives.
 
(1) Water-based polymer emulsion
Mainly acrylic acid, ethylbenzene synthesis. The function is to transfer the pigment carrier, providing adhesion, hardness, brightness, drying speed, wear resistance, water resistance. The film forming emulsion is applied to the surface printing of non-absorbent substrate. Non-film forming emulsions are used for printing absorbent materials such as paper and board.
 
(2) Pigments
Organic pigments are phthalocyanine blue, Lisol red; Inorganic pigments are carbon black, titanium dioxide.
 
(3) surfactants
The function is to reduce the surface tension, so that the ink on the substrate auxiliary expansion, improve the stability of the ink.
 
Prevention of ink thixotropy
·The performance of ink thixotropy and the influence of printing quality
 
Some inks in the transmission process, due to the thixotropy is too large, in its thixotropy phenomenon before its high viscosity, printing is easy to cause blocking ink, paste plate failure. Therefore, some printing presses are equipped with agitators in the ink hopper to stir the ink to make it "thixovariable" and improve the flow of the ink, reduce the viscosity of the ink, in order to prevent the phenomenon of ink blocking and paste. The thixotropy of the ink is too large, the ink in the printing process is more and more thin, the ink color of the printing is more and more light, and it is almost impossible to adjust, this ink is not suitable for printing the full plate of the printing field, and this problem should be paid attention to when printing.
 
It can be said that ink thixotropy discomfort has a great impact on printing quality. We found that in the printing process, especially in the case of low temperature and slow machine speed, the ink in the ink hopper often appears not smooth delivery, abnormal ink supply, resulting in the ink color of the printing is becoming lighter and lighter, which affects the stability of the printing ink color, which is the main manifestation of poor thixotropy of the ink. In this regard, we should pay attention to often stir the ink in the ink tank, so that it maintains continuous and uniform fluidity, and ensure the quality of the ink color of the product.
 
·Technical measures for controlling ink thixotropy
 
Printing requires that the ink has proper thixotropy, and too much thixotropy of the ink will have a bad effect on printing. The thixotropy of the ink is mainly determined by its material properties, but as mentioned earlier, the printing conditions will also affect the thixotropy of the ink to a certain extent. Therefore, when the inherent thixotropy of the ink cannot achieve normal printing, the corresponding control can be carried out through process technical measures.
 
For example, when printing, the appropriate ink fluidity can be adjusted according to the characteristics of the printing machine and the temperature. When the printing speed is low and the temperature is low, due to the small thixotropic of the ink, its fluidity is also small, which is not conducive to the uniform transfer of ink and ink, then the ink can be properly diluted a little to meet the requirements of the printing process.
 
In order to prevent too much "thixotropy" of ink and bring adverse effects to printing, it is necessary to control the printing process conditions so that the thixotropy of ink is controlled within the range of printability.
 
①Try to print in a constant temperature and humidity environment, and install air conditioning equipment for the production workshop. If the conditions are limited, when the climate is dry and the wind is strong, the doors and Windows of the workshop can be closed to prevent the ink from thickening and becoming sticky;
 
②In the case of excessive thixotropic ink itself, it is necessary to try to control the printing speed in the lowest range, in order to reduce the temperature of the ink due to the large friction coefficient of the machine, so that the ink becomes thinner;
 
③Under the condition of not affecting the uniform layout and sufficient inking, it is necessary to minimize the number of ink rollers used on the machine to reduce the coefficient of friction during printing;
 
④Adjust the position of the ink roller and the water roller on the machine to prevent the contact between the ink roller and the ink roller, the ink roller and the page or the water roller and the page from being too tight, and the abnormal temperature rise caused by the large friction coefficient will make the ink thin;
 
⑤Control the stroke of the ink roller rotation, if the ink roller rotation stroke is large, the temperature is high, and the ink is easy to become thin. Therefore, in the case of high printing speed, the rotation stroke of the ink bucket roller should be reduced as much as possible, and the gap between the ink bucket steel sheet and the ink bucket roller should be adjusted to meet the requirements of printing ink supply;
 
⑥When the printing plate (including flexographic) is large, the printing speed should be controlled lower to reduce the friction temperature;
 
⑦ Choose a reasonable printing ink, printing network plate requires the thixotropy of the ink slightly larger, and printing a large area of the field version of the ink thixotropy is slightly smaller, so as to better improve the printing quality.
 
Disclaimer: This article is reproduced on our website to provide readers with more news information. The content does not constitute investment, consumption advice, only for readers' reference