In the use of water-based humor, we all know that if the water-based ink drying is too slow, it will cause the prints to dry badly, the ink sticks to the guide roller, the prints lose luster, it will also affect the overprint effect, resulting in print quality problems. However, if the water-based ink dries too quickly, it will transfer badly, and it will easily cause blockages. The edge of the imprint will appear jagged and the ink will dry to the surface of the plate. If the water-based ink dries too fast, it will also cause scratches on the surface of the printed matter when printing the cable screen. The reason is that the ink has not yet penetrated the surface of the printing material and it has dried, causing the ink to float on the surface of the printing material. Drop it. Therefore, water-based ink drying is a crucial issue. Here are some technical guidances for its drying problems for your reference! !
For the drying problem of flexo-based water-based inks, there are the following technical guidelines:
First, as far as possible without affecting the printing speed, try to make ink drying slower during the printing process. This can be adjusted by adding a slowing agent. The amount of slow-drying agent that different manufacturers need to add ink is different, generally not more than 5%. The ink thickens and the pH decreases when the slow drying agent is added. Therefore, water and stabilizers are added to control the viscosity and pH of the ink while the slow drying agent is added.
Second, properly increase the pH of the ink to reduce the drying speed of the printing process without affecting the drying speed. The pH is generally controlled at 8.5-9.5. The drying is too fast, and the pH is controlled to be above 9 by adding a stabilizer, but it cannot exceed 9.5, otherwise the ink properties will change. The surface tension of the ink is low, and the screen version is more likely to block, drying will become more slowly.
Third, when printing thin paper products, reducing the drying speed of the ink can reduce the warpage of the paper. This usually requires the addition of slow drying agents or retarders. The reason is that water and alcohol in the ink after the printing of the water-based ink are volatilized, so that the middle of the paper is loosened and warped. The effect of the slow drying agent is to allow the ink to not dry out instantaneously and reduce warpage.
Fourth, enhance the convection speed of the air in the oven, which can significantly speed up the drying of the printed matter. Due to the large amount of water and alcohol contained in the aqueous ink, enhanced convection can reduce the relative humidity in the oven and accelerate the evaporation of the solvent.
Fifth, we use high-ink density inks and higher-line anilox rollers when printing inks with large amounts of ink. This is beneficial to the drying of prints, and it can also reduce the appearance of water marks.
Sixth, adding a slow-drying agent can solve the print scratches and the surface of the varnish plate. If the ink dries too quickly, it will cause the ink to dry on the surface of the printing material without entering the permeation stage. As a result, the adhesion will not be enough, and the ink layer will fall off easily. When the ink is overprinted or glazing, the ink of the previous color will stick out. This can also be adjusted by changing the color sequence or decreasing the ink viscosity.
Seventh, adding slow-drying agent and speeding up can reduce the blocking phenomenon. Too slow a printing speed will cause the ink to spread on the plate, causing the dots to stick. However, if the ink dries too fast, the ink will not be fully transferred, causing ink deposits around the dots and blocking the plate.
Eighth, the paper guide roller heats up and can also speed up the drying speed of the printed matter. When we print products with a large amount of ink, if the drying capacity of the printing press is limited, each time we just start the speed is not fast, after a certain period of time there will be some room for improvement, this is the cause of the heat of the paper guide roller. . After the paper guide roller heats up, the ink does not easily stick to its surface. Before starting the machine, an independent drying device is opened in advance, and the opening device can turn off the suction device first, so that the device can accumulate the maximum heat in the shortest time. Speed ​​can be increased quickly.
The ninth, higher printing speed required ink viscosity is lower, which is conducive to the transfer of ink.
For the drying problem of flexo-based water-based inks, there are the following technical guidelines:
First, as far as possible without affecting the printing speed, try to make ink drying slower during the printing process. This can be adjusted by adding a slowing agent. The amount of slow-drying agent that different manufacturers need to add ink is different, generally not more than 5%. The ink thickens and the pH decreases when the slow drying agent is added. Therefore, water and stabilizers are added to control the viscosity and pH of the ink while the slow drying agent is added.
Second, properly increase the pH of the ink to reduce the drying speed of the printing process without affecting the drying speed. The pH is generally controlled at 8.5-9.5. The drying is too fast, and the pH is controlled to be above 9 by adding a stabilizer, but it cannot exceed 9.5, otherwise the ink properties will change. The surface tension of the ink is low, and the screen version is more likely to block, drying will become more slowly.
Third, when printing thin paper products, reducing the drying speed of the ink can reduce the warpage of the paper. This usually requires the addition of slow drying agents or retarders. The reason is that water and alcohol in the ink after the printing of the water-based ink are volatilized, so that the middle of the paper is loosened and warped. The effect of the slow drying agent is to allow the ink to not dry out instantaneously and reduce warpage.
Fourth, enhance the convection speed of the air in the oven, which can significantly speed up the drying of the printed matter. Due to the large amount of water and alcohol contained in the aqueous ink, enhanced convection can reduce the relative humidity in the oven and accelerate the evaporation of the solvent.
Fifth, we use high-ink density inks and higher-line anilox rollers when printing inks with large amounts of ink. This is beneficial to the drying of prints, and it can also reduce the appearance of water marks.
Sixth, adding a slow-drying agent can solve the print scratches and the surface of the varnish plate. If the ink dries too quickly, it will cause the ink to dry on the surface of the printing material without entering the permeation stage. As a result, the adhesion will not be enough, and the ink layer will fall off easily. When the ink is overprinted or glazing, the ink of the previous color will stick out. This can also be adjusted by changing the color sequence or decreasing the ink viscosity.
Seventh, adding slow-drying agent and speeding up can reduce the blocking phenomenon. Too slow a printing speed will cause the ink to spread on the plate, causing the dots to stick. However, if the ink dries too fast, the ink will not be fully transferred, causing ink deposits around the dots and blocking the plate.
Eighth, the paper guide roller heats up and can also speed up the drying speed of the printed matter. When we print products with a large amount of ink, if the drying capacity of the printing press is limited, each time we just start the speed is not fast, after a certain period of time there will be some room for improvement, this is the cause of the heat of the paper guide roller. . After the paper guide roller heats up, the ink does not easily stick to its surface. Before starting the machine, an independent drying device is opened in advance, and the opening device can turn off the suction device first, so that the device can accumulate the maximum heat in the shortest time. Speed ​​can be increased quickly.
The ninth, higher printing speed required ink viscosity is lower, which is conducive to the transfer of ink.
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