The Performance of Digital Printing Reactive Ink and Its Application

The so-called digital active ink is actually a liquid reactive dye. It is an ink that is widely used in digital printing applications. It has the advantages of wide adaptability of fabrics, good color fastness, and easy use. It can be applied to cellulose at present. Fibers, protein fibers and other fabrics. Its main components are:

Dyes 2-15%
Deionized water 45-95%
PH buffer 0.1-0.5%
Bactericide 0.1-0.5%
Surfactant 15-45%

Surfactant has two functions. One is to control the surface tension of ink and make it adapt to the requirements of digital printing machines. Piezoelectric ESPON nozzles which are widely used now have high requirements on viscosity and surface tension, and if the viscosity is too high, they are easy to clog. If the nozzle is too low, the ink will be thrown off and the secondary cloth will be formed. Generally, the viscosity is controlled at 10-50 mPa.s and the surface tension is controlled within 30-60 dyne/cm. This ensures that the dye can penetrate into the fiber. It can also maintain the fineness of the flower pattern; in addition, the surfactant can help the dye to dissolve and increase the liquid dye's strength. Surfactants are generally selected from glycols or sulfonic acids. For example, CIBA MI series inks are homologs of propylene glycol and sodium naphthalene sulfonate.

The function of the bactericide is to prevent the mold from forming in the ink path of the digital printing machine and block the ink channel. In the early days of digital printing, similar situations occurred in Europe. In order to ensure the stability of the dye solution, it is necessary to control the PH value of about 8. In liquid dyes, controlling the content of inorganic salts is also very important, so deionized water must be used in the dye liquor preparation process, and other additives must also use nanofiltration to remove inorganic salts. The content of inorganic salt can be detected by measuring its conductivity, and the control value is less than 2000 uΩ/cm. For insoluble disperse dyes, when the concentration of inorganic salt increases, there will be more charges that are electrically negative with the adsorption layer into the adsorption layer. When the adsorption layer charge is completely neutralized, the zeta potential in the micelle drops to zero, the electrostatic repulsive force of the micelle decreases, or even disappears completely, which greatly reduces the anti-agglomeration ability of the dispersion and stabilizes the entire dispersion system. Sexual damage, causing dye sedimentation. In addition, an excessively high concentration of inorganic salt can easily corrode the nozzle and reduce the service life of the nozzle.

At present, the digital active inks commonly found in the domestic market include blue, black, magenta, blue, orange, yellow, and gray. In addition, blue and magenta are diluted to about 15-20% to make light blue and light red. Can meet the basic production needs, but there are still problems in the application of blocking the nozzle, hair color instability, shading is not correct, the depth is not enough, the color gamut is too small and so on.

Causes of nozzle clogging are caused by the reasons of digital printing machines and dyes. Machines are mainly caused by interruption of ink supply, blockage of ink mold, ink barrier of the ink cartridge, and other reasons. The main reasons for dyes are dye deposition, impurities, and excessive solubility of dyes. For insoluble disperse dyes, the dye particle size is also critical, and its particle size requires that no more than 10 particles exceed 0.2 μm in the microscope's 0.1 mm field of view. The clogging nozzles are mainly black, blue, magenta, and cyan, of which the black is the most severe, especially when printing large ink backgrounds. This is not only related to its dye matrix structure, but also to the phenomenon of nozzle clogging being significantly improved after the concentration of lanthanum and yttrium (11) and lanthanum hexachlorodimethoate is 0% or more. However, at present, black ink itself has the problem of insufficient strength and low color depth. Therefore, there are certain disadvantages in reducing the dye solubility to improve plugging. When the ink is left for more than 3-6 months, it is also easy to produce clogging of the nozzle. Before use, it is filtered by two layers of Buchner funnel filter. In addition, some inks will have agglomeration phenomenon. Once the ink channel leaks slightly, it will cause a large area of ​​nozzle clogging. To know whether the ink will produce granules, drop a drop of ink onto the film paper, place it in the air to volatilize naturally, and watch its residue. If it is lumpy, it will result in nodulation. Otherwise, will not.