Production and Treatment of "Initiating Flower" Phenomenon in Compound Ink

The phenomenon of “flowering” refers to the fact that the printed product should be in a continuous solid part, but due to the irregular transfer of ink in the pattern, a fine groove line appears in the solid part, and the solid part cannot be smoothly and smoothly printed. After the printing, part of the field was imprinted with an uneven orange peel. In addition, part of the graphic text is imaginary. The reasons for this are as follows:

1, moisture effects. There are two main sources of moisture: First, the diluent contains moisture, and especially toluene is easy to have a certain amount of moisture. The second is condensate water, because the solvent evaporates too quickly (in this case, the ink surface is easily crusted). When the volatilization absorbs heat, the surface temperature of the ink is reduced. Humid air with high humidity and high temperature will condense on the surface of the ink to form a layer of condensation. Water, if carefully observed, will have many small droplets on the surface of the ink crust, and this moisture will also enter the ink inside. During the printing, as the moisture in the ink accumulates, the moisture will peel off the resin in the ink and emulsify the resin. The ink becomes a water-in-oil (W/O) structure, and the pigment particles coated with anthraquinone resin are replaced by water and exposed. During the collision, they gradually aggregated and became thicker (blocking the mesh). Therefore, the macroscopic observation of the ink revealed that the ink became sticky, thickened, roughened, and unsmooth; a large amount of precipitate accumulated at the bottom of the ink tank (the white ink was the most obvious due to titanium dioxide. Hydrophilicity is the strongest; there is also a thin layer of cloudiness on the non-graphical part of the printing plate), the total scraping is not clean (if the squeegee pressure is increased, the printing plate is worn); the printing plate on some printing presses At both ends, the gel-like resin gradually transitions to the embossing cylinder, and the thicker it is, the gap between the embossing cylinder and the printing plate is increased, the color registration is inaccurate, and the embossing roller is damaged. The amount of ink transferred on the prints is getting less and less, the more printed the more shallow, not colored. As the effect of moisture on the ink makes the ink into an inhomogeneous body, the printed product appears "flowering" and leaking bottom. The moisture content of the diluent can be initially tested with a "moisture test agent" which is sold at New Oriental Ink Co. and can not be used with thinner than water content. In addition, the temperature and humidity of the printing shop should also be controlled within the standard range.

2, true solvent evaporation. The fact that the true solvent volatilizes too quickly during the printing process causes insufficient amounts of true solvent in the ink to cause the following two problems: First, the resin precipitates. This problem has a significant effect on some types of inks, such as polyurethane type inks. Precipitation of the resin causes the ink to become viscous, thickened, and thick, which causes a series of changes in the printing product such as “flowering” and inaccurate printing. This is similar to the effect of moisture on the ink. Second, the re-dissolution of the ink deteriorates. In normal printing, only about 2/3 of the ink is transferred to the substrate when the ink in the plate mesh contacts the substrate, and 1/3 of the ink remains in the mesh. As the solvent volatilizes, the remaining ink in the mesh becomes dry. At this time, if the ink on the back side has poor re-solubility of the ink in the front, the dry solid ink in the net will accumulate more (ie, the burying plate), and less ink will be transferred to the substrate. Ink and ink can not completely cover the bottom of the ink, there is a "flower" phenomenon. For this type of ink, a portion of the true solvent should be added separately during printing and the proportion of each solvent in the diluent should be adjusted.

3, the printing operation is not appropriate. When printing, it is necessary to coordinate the balance of printing speed, press pressure, squeegee pressure and angle, ink viscosity, ink density, and ink dryness. If the printing speed is faster, the faster the ink is dry, the lower the ink viscosity, and the higher the ink density, and vice versa. If the viscosity of the ink is high, the printing speed is fast, or the viscosity of the ink is low, the printing speed is slow, and both of these situations easily cause the printed product to “sweet”. The speed of the printing press is 100-120 m/min, and the viscosity should be controlled between 17-18 seconds for color ink and 14-16 seconds for white ink (Carn 3 cup); at 50-80 m/minute, the color ink is 20- In 22 seconds, white ink is 18-20 seconds. At the same time, these conditions also need to consider the grade of the ink and the texture of the printing plate. If the printing speed is fast, the viscosity must be required to be low. If the ink concentration is too low at the same time, the printing product will inevitably leak at the bottom. Similarly, when the printing speed is slow and the drying is fast, it is easy to cause a paste plate; otherwise, it is easy to cause anti-sticking or solvent residue.

4. The ink and plate are not properly selected. If the printing requirements are high and the printing speed is high, the high-grade ink should be used. This requires the ink to have a high color density and a low viscosity, which can achieve a good transfer effect. Take New Oriental ink as an example. If high-speed machines print PET and nylon, they should use Type 322 ink, but not 321F type ink. For printing BOPP substrates, 200S type ink should be used, preferably 211K type ink. If low-speed machines print PET and nylon, they should use 321F inks, and BOPP use 200SA inks. When the ink is selected, according to the product requirements for the version of the web have certain requirements, as the saying goes 3 minutes 7 points version of the ink, when the plate is not good, when printing is difficult to use ink performance does not make up for the version Shortcomings. Under normal circumstances, the white version of the number of lines 175 lines, 35μ depth, some manufacturers may require deeper version because the version as the leading product, large quantities, long service time requirements. However, when the version is deepened, the outlets will have to be increased. Relatively speaking, the number of lines will be reduced and the width of the nets will increase. As a result, the phenomenon of “flowering” can easily occur during printing.

5, ink is poor. Mainly in the following two aspects: First, the ink is too dry, the ink easily dry knot in the pocket, so that the small print or pattern can not be printed, this phenomenon also known as paste. Slow-drying solvent is applied at this time to adjust the dry speed. The second is that the ink is thixotropic, thick and poorly leveled. After the ink is transferred to the substrate, it spreads and the printed product shows "flowering." This type of ink should be replaced.

(New Oriental Ink Group Co., Ltd. Wang Dazhi Wang Dexin)