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What precautions should be taken when using water-based inks?
Preferably choose purified water (or distilled water) as the main solvent. If tap water is chosen as the main solvent, it is necessary to conduct hardness testing on the tap water. Depending on the actual production situation, small amounts of solvents such as ethanol or isopropanol can be added during the solvent ratio, but if the proportion is too high, it may reduce the re-dissolvability of the resin and cause printing failures such as plate blocking.
Author:
The application of water-based ink for cigarette packaging has the following precautions summarized during the application process:
1. Plate making requirements
The printing plate should preferably use electronic engraving or laser engraving, with a cell depth of 15 to 25 μm.
2. Selection of solvents and control of ink viscosity
Pure water (or distilled water) should be prioritized as the main solvent. If tap water is chosen as the main solvent, it needs to be tested for hardness. Depending on the actual production situation, small amounts of ethanol, isopropanol, and other solvents can be added during the solvent mixing, but excessive proportions will reduce the resin's re-dissolvability, leading to printing failures such as plate blocking.
Control the ink viscosity to 15 to 25 seconds (coating 3 cups) by adding solvents like water. The specific viscosity should be determined based on printing speed, plate cell depth, color hue of the printed product, and other process conditions.
Before formal printing, adjust the ink viscosity according to the plate cell depth, and during the printing process, try not to add water to the ink; only new ink should be added to ensure consistency in color hue and concentration before and after printing.
3. Reasonable use of various additives to improve the printability of water-based inks
① Defoamer: Used to eliminate foam in water-based inks, generally used at 1% to 2%. Generally, when the viscosity of water-based ink is too high, the pH value is too low, or the printing speed is fast, and the hardness of the main solvent water is high, bubbles are likely to form. Excessive bubbles can lead to printing defects such as white spots, ink splashes, and uneven ink color.
② Stabilizer: Also known as pH stabilizer, the main component is organic amines. The stabilizer is mainly used to adjust and control the pH value of water-based inks, keeping it stable at 8.0 to 9.5, at which point the printability of the water-based ink is good. When the pH value of the water-based ink exceeds 9.5, it becomes too alkaline, reducing the viscosity, slowing the drying speed, and decreasing water resistance; when the pH value is below 8.0, it becomes too weakly alkaline, increasing viscosity, causing the ink to dry easily and accumulate on the plate, leading to dirty plates, blocking, and foam generation, while also reducing water resistance. Generally, during the printing process, an appropriate amount of stabilizer should be added at regular intervals to stabilize the pH value of the water-based ink, while also adjusting the viscosity and diluting the ink.
③ Diluent: Mainly used to reduce the viscosity of water-based inks, the amount should be controlled within 3% to prevent the hue of the water-based ink from becoming lighter, while keeping the pH value unchanged. The diluent should be added slowly while stirring to prevent the viscosity of the water-based ink from becoming too low.
④ Slow-drying agent: The slow-drying agent can inhibit and slow down the drying speed of water-based inks, preventing the ink from drying and solidifying in the plate cells, thus reducing the occurrence of printing failures such as plate blocking and smudging. The amount is generally controlled at 1% to 2%. If used excessively, the ink layer may not dry completely, leading to dirty backsides or odors in the printed products.
⑤ Fast-drying agent: Used to accelerate the drying speed of water-based inks, with a dosage of 0 to 3%.
⑥ Thickener: Used to increase the viscosity of water-based inks, with a dosage of 0.5% to 1%.
4. Depending on the characteristics of the printed product, consider using a combination of water-based inks and solvent-based inks for printing. For example, use alcohol-soluble, ester-soluble, or UV inks for printing fine line plates and halftone plates, and use water-based inks for printing color blocks and bold line plates.
5. If an abnormal shutdown or temporary shutdown occurs during the printing process, try to keep the printing plate rotating at a low speed, as water-based inks are prone to drying and blocking in a stopped state (the main reason is the poor affinity between water and the binder, making it easy for water to separate, while the binder film makes it difficult for water to re-dissolve). When water-based ink dries and blocks the plate, first use a water-based ink cleaner to moisten the plate, then brush the plate with a fiberglass brush. The main components of the water-based ink cleaner are approximately 3% sodium silicate, 1% sodium hydroxide, about 2% organic amines (one or more of compounds such as polyethylene amine, triethanolamine, diethylaminoethanol, dimethylaminoethanol, aminomethyl ethanol), about 10% alkaline penetrant OEP-70, and about 80% water.
1. Plate making requirements
The printing plate should preferably use electronic engraving or laser engraving, with a cell depth of 15 to 25 μm.
2. Selection of solvents and control of ink viscosity
Pure water (or distilled water) should be prioritized as the main solvent. If tap water is chosen as the main solvent, it needs to be tested for hardness. Depending on the actual production situation, small amounts of ethanol, isopropanol, and other solvents can be added during the solvent mixing, but excessive proportions will reduce the resin's re-dissolvability, leading to printing failures such as plate blocking.
Control the ink viscosity to 15 to 25 seconds (coating 3 cups) by adding solvents like water. The specific viscosity should be determined based on printing speed, plate cell depth, color hue of the printed product, and other process conditions.
Before formal printing, adjust the ink viscosity according to the plate cell depth, and during the printing process, try not to add water to the ink; only new ink should be added to ensure consistency in color hue and concentration before and after printing.
3. Reasonable use of various additives to improve the printability of water-based inks
① Defoamer: Used to eliminate foam in water-based inks, generally used at 1% to 2%. Generally, when the viscosity of water-based ink is too high, the pH value is too low, or the printing speed is fast, and the hardness of the main solvent water is high, bubbles are likely to form. Excessive bubbles can lead to printing defects such as white spots, ink splashes, and uneven ink color.
② Stabilizer: Also known as pH stabilizer, the main component is organic amines. The stabilizer is mainly used to adjust and control the pH value of water-based inks, keeping it stable at 8.0 to 9.5, at which point the printability of the water-based ink is good. When the pH value of the water-based ink exceeds 9.5, it becomes too alkaline, reducing the viscosity, slowing the drying speed, and decreasing water resistance; when the pH value is below 8.0, it becomes too weakly alkaline, increasing viscosity, causing the ink to dry easily and accumulate on the plate, leading to dirty plates, blocking, and foam generation, while also reducing water resistance. Generally, during the printing process, an appropriate amount of stabilizer should be added at regular intervals to stabilize the pH value of the water-based ink, while also adjusting the viscosity and diluting the ink.
③ Diluent: Mainly used to reduce the viscosity of water-based inks, the amount should be controlled within 3% to prevent the hue of the water-based ink from becoming lighter, while keeping the pH value unchanged. The diluent should be added slowly while stirring to prevent the viscosity of the water-based ink from becoming too low.
④ Slow-drying agent: The slow-drying agent can inhibit and slow down the drying speed of water-based inks, preventing the ink from drying and solidifying in the plate cells, thus reducing the occurrence of printing failures such as plate blocking and smudging. The amount is generally controlled at 1% to 2%. If used excessively, the ink layer may not dry completely, leading to dirty backsides or odors in the printed products.
⑤ Fast-drying agent: Used to accelerate the drying speed of water-based inks, with a dosage of 0 to 3%.
⑥ Thickener: Used to increase the viscosity of water-based inks, with a dosage of 0.5% to 1%.
4. Depending on the characteristics of the printed product, consider using a combination of water-based inks and solvent-based inks for printing. For example, use alcohol-soluble, ester-soluble, or UV inks for printing fine line plates and halftone plates, and use water-based inks for printing color blocks and bold line plates.
5. If an abnormal shutdown or temporary shutdown occurs during the printing process, try to keep the printing plate rotating at a low speed, as water-based inks are prone to drying and blocking in a stopped state (the main reason is the poor affinity between water and the binder, making it easy for water to separate, while the binder film makes it difficult for water to re-dissolve). When water-based ink dries and blocks the plate, first use a water-based ink cleaner to moisten the plate, then brush the plate with a fiberglass brush. The main components of the water-based ink cleaner are approximately 3% sodium silicate, 1% sodium hydroxide, about 2% organic amines (one or more of compounds such as polyethylene amine, triethanolamine, diethylaminoethanol, dimethylaminoethanol, aminomethyl ethanol), about 10% alkaline penetrant OEP-70, and about 80% water.
Key words:
Distillation,Solvent
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Shaanxi Xinaohua Material Technology Co., Ltd
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