Question 1: blocking
In the use of water-based ink, blocking is the most common problem, mainly because of the poor re solubility of gravure water-based ink, so once improper operation, it is very easy to block the plate. And blocking will cause a series of printing quality problems, such as pinholes on the surface of the printed matter, short of small characters, uneven ink color, leakage and so on. The causes and solutions of blocking are as follows.
(1) Intermittent stop version, ink due to the evaporation of diluent and dry solid in the network. At this time, it is necessary to use special tools and cleaning agent to clean the plate. If necessary, remove the plate and use organic solvent (ethyl acetate) to clean it. Therefore, in the case of intermittent downtime, it is recommended to use the way of non-stop version, so as to avoid ink drying in the mesh.
(2) Ink due to drying too fast and instant dry solid in the network. In this regard, a small amount of slow drying agent can be added into the ink, slow drying agent can inhibit and slow down the ink drying time, prevent the ink surface crust, the general dosage is controlled at 3% - 5%; Secondly, consider whether the diluent ratio is appropriate, and adjust the diluent ratio if necessary. Generally, the ratio of alcohol and water in water-based ink diluent is between 1:1 and 4:1, but the amount of water needs to be considered when increasing the water proportion. If the amount of water is too much, on the one hand, it will produce too many bubbles, on the other hand, it will lead to ink drying is not complete, making the printed matter sticky or ink Pull back phenomenon.
(3) The ink viscosity is too high. At this time, the ink viscosity should be appropriately reduced, but the printing speed and leveling must be considered. Because the viscosity of the ink is too low, there will be too many bubbles, resulting in white spots on the surface of the printed matter, the color of the printed text is too light or the thin lines and small characters become thick.
(4) The printing plate is too shallow. At this time, we should properly deepen the depth of the printing plate mesh, but we must consider the quality problems when the printing plate mesh is too deep, such as thicker handwriting, fuzzy small words, unclear patterns and so on.
Problem 2: poor drying
Drying performance is one of the most important indicators of water-based ink. The drying speed of water-based ink is slower than that of solvent-based ink. Once the drying is not sufficient, it will produce stick roller phenomenon.

Therefore, in the use of water-based ink drying temperature must be increased, usually 10 ~ 20 ℃ higher than the solvent based ink drying temperature, but also need to increase the exhaust air, conditional conditions can be extended after printing paper path channel. Of course, the improvement and improvement of water-based ink drying performance also needs the cooperation of ink manufacturers to adjust the water-based ink formula.

Problem 3: dirty brace on the plate
In the production of water-based ink gravure printing, there are often dirty bands around bar code or dark color pictures and texts because the ink on the corresponding position is not scraped clean. This is mainly because the lubricity of water-based ink is lower than that of solvent based ink.
In this regard, ink manufacturers need to add the corresponding auxiliaries in the production of water-based ink to solve this problem. At the same time, printing workers are required to adjust the angle and pressure of the scraper in printing production. The shorter the blade is, the better the scraping effect is. If conditions permit, printing enterprises can consider using ceramic scraper, which has smooth blade, no need to polish, good elasticity, corrosion resistance, and the blade part after unique polishing treatment, can fit perfectly with the printing plate cylinder, so as to achieve the best scraping effect.
Problem 4: too many bubbles
Excessive bubbles of water-based ink will lead to white spots, sand holes, water marks and other phenomena on the surface of printed matter. The causes and solutions of bubble problem are as follows.
(1) Dilute water-based ink when adding more water. In this regard, two solutions can be adopted: one is to add defoamer, which is generally 0.5% - 1.0%; the other is to adjust the proportion of diluent.
(2) Some dark water-based ink due to the use of too little and long-term circulation, so that the diluent of alcohol volatilization, more water. At this time, appropriate amount of alcohol should be added.
(3) The dosage of surfactant is not controlled properly. Surfactant can reduce the surface tension of water and improve the wettability of pigment, but if the dosage is not properly controlled, a large number of bubbles will be produced. The amount of surfactant should be controlled by the ink manufacturer in the production process.
Problem 5: poor print leveling
Water based ink leveling performance is mainly reflected in the water ripple phenomenon is heavy or printing is not true (leakage), the causes and solutions are as follows.
(1) The viscosity of the ink is too low, which leads to the weakening of the ability of the carrier to drive the pigment. At this time, the ink viscosity should be appropriately increased, but if the ink viscosity is too high, the ink liquidity will be poor, printing leveling will also be poor. In general, when using water-based ink for gravure printing, the viscosity of full plate printing should be basically the same or slightly lower than that of solvent based ink, and the viscosity of halftone image printing should be slightly lower than that of solvent based ink.
(2) After a long time of circulation, the binders in the water-based ink decrease or the amines volatilize, which leads to the change of the performance of the water-based ink, and the printing leveling will also be poor. When the problem is minor, a large number of new ink can be added to solve; when the problem is serious, such as water-based ink is contaminated, it is necessary to replace the new ink.
Problem 6: poor stability
The poor stability of water-based ink is mainly reflected in the phenomenon of easy precipitation, delamination and false stickiness, which is mainly due to the poor dispersion of pigment in the water-based resin, easy aggregation and precipitation, and the need to add additives (surfactant, defoamer, pH stabilizer, leveling agent, slow drying agent, fast drying agent, dispersant, diluent, etc.) to improve its own weakness, so as to improve its own weakness As a result, its stability becomes worse.
In this regard, before using water-based ink, it is necessary to fully stir it. For example, when using new ink, it should be stirred evenly in advance, and then the diluent should be added for adjustment; in the printing process, it should also be stirred regularly to prevent the ink precipitation and produce dirty stretch or blocking. Occasionally encounter difficult to stir the coagulation of water-based ink for colloidal state, you need to consider the quality of the ink itself.
Precautions for use
1. Clean the plate
When the new version is used for the first time, it is necessary to clean the oil stains on the surface with alcohol to prevent the water-based ink from polluting; after printing, the printing plate should be thoroughly cleaned with special cleaning agent, and then put into the plate box after being dried with dry cloth; when the new version is used next time, it is still necessary to wipe with alcohol before using the machine to prevent the ink from drying in the mesh.
2. Shutdown requirements
In case of intermittent shutdown, the mode of stop without stop is adopted, and the scraper is released at the same time. If you need to shut down for a long time, use alcohol to clean the plate, in order to prevent the ink drying in the hole.
3. Recycling of residual ink
After the end of each production, the remaining mixed water-based ink should be filtered, otherwise the next use will be due to dust fall, crust dry solid, paper fiber fall into and produce dirty brace or block plate. The filtered water-based ink should be put into the plastic bucket sealed storage, in order to prevent amine volatilization.
4. Proper amount of ink
Water based ink in a long cycle, due to a large number of amine volatilization and lead to poor stability. In order to avoid this problem, we should try our best to match a few inks and add new inks according to the principle of "frequently adding less".
The application of water-based ink in gravure printing field will be more and more extensive. As production personnel, we must be familiar with the printing characteristics and printability of water-based ink, understand the common problems, causes and solutions of water-based ink in the printing process, and master the matters needing attention in the use of water-based ink, so as to ensure the product quality. 】、
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