Application of water-based ink in carton carton printing
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In the call to protect the environment, save energy, reduce pollution and recycle and safe production. China's packaging printing water-based inks ranked first in other packaging printing inks in just a few years with 35% of their use. The more high-grade packaging printing inks, especially water-based printing inks, the stronger the printing characteristics and the narrower the range of adaptation. From ordinary batter starch, dextrin to shellac, casein, sodium lignin; from rosin-modified maleic acid resin to styrene-acrylic copolymer resin, even polymer emulsion resin with core-shell structure and network structure . They are all called water-based inks without exception.
In China, the number of inks used in packaging and printing products is increasing every year, especially in the form of screen stencils and flexible embossing, but most of them are paper substrates for absorbing media and are gravure printing. In particular, plastic and aluminum foil substrates used in non-absorbent media have only recently realized that rotary machines are printing on reel materials. The advancement of this technology shows that ink and wash has become increasingly mature. At present, ink has been identified as "non-toxic ink" by the US Food and Drug Administration.
The speed of development of ink makes other inks hard to find. In the past, the ink on the paper has poor gloss, water resistance, poor adhesion, difficulty in overprinting, discoloration and fading, and the product is easy to warp and the uneven angle has been improved. This is very advantageous for promoting the application of aqueous inks in cartons and cartons. In addition, the ink has the characteristics of no explosion, no transportation danger ‘no pollution, no toxicity, etc. and uses water to adjust the drilling degree and clean the printing equipment, which reduces the production cost and labor intensity. And to reduce the safety hazards for production and transportation and use of units. The current use of ink is increasing, and despite the quality, there are still some shortcomings, but the safety is recognized by the packaging and printing industry.
For more than ten years, ink and wash have combined the characteristics of various packaging and printing materials in the trial printing and production application of manufacturing, and have firmly grasped: 1 The film-forming substance in the ink adheres the pigment filler to the substrate. And the ink is provided with a non-stick body; 2 can make the ink have sufficient leveling, spreadability and gloss on the printing material; 3 has high-efficiency wetting agent and wear resistance: 4 maintain and improve the pigment Dispersion and printability; 5 can have sufficient printing resolubility, but have a certain water resistance after drying. The conventional ink is changed to use a simple water-soluble polymer compound such as casein, shellac, polyvinyl alcohol resin or the like as an ink binder, which is not resistant to friction and water. Therefore, for the rotary flexible embossing and gravure ink systems, aqueous ink binders such as acrylic acid and polyacrylic acid vinegar have been used, which have been derived from the past glycol ethers (which metabolize to produce harmful substances such as alkoxyacetic acid). Changed from the propylene glycol ether series (metabolism to produce almost non-toxic 1,2-propanediol. Finally decomposed into carbon dioxide and water, the toxicity is very low. There is also a non-initiator aqueous UV ink that will enter the market) to prepare non-toxic ink. Most of the latter are now used.
Relationship between printing conditions and dry speed and gloss
1. Water-based ink for printing water-filled flexible letterpress and rotogravure webs for packaging paper bags, books, cartons, cartons, cigarette packets, and more than a decade. Although the gravure paper ink produced by the high polymer acrylic resin can meet the printing requirements of high-grade products with high printing quality requirements, it is really recommended to use the water-free UV ink without initiator.
2. The temperature and humidity of the printing workshop have a great influence on the drying speed and gloss of the printed ink film. Temperature is the main factor affecting oxidative polymerization, volatilization, and strong ink film. Therefore, in the summer and winter southern coastal and northern plateau regions, the difference in gloss after ink drying and film formation is about 1 time. In the two cases where the relative humidity reaches 95% and 65%, the drying time is almost twice different, and the dryness and pH of the paper and the paper box itself directly affect the drying time of the printed product.
3. Acidity can delay the formation of oxidative polymerization and volatilization of the ink film. Excessive alkalinity will result in internal wetness and dryness, which will affect the adhesion of the ink to the surface of the printed product.
4. Because oxygen or blowing or baking is a factor that promotes oxidative polymerization and volatilization of strong ink films, the degree of ventilation in the pressroom and the way in which the prints are stacked are also related to the drying speed of the printed product.
Causes and troubleshooting of ink and wash
1. Hue is not allowed. The ink drilling degree is too low or the pigment content in the ink system is small or the color purity is deviated. The ink is analyzed and precipitated during printing, and the transfer is poor. Incorporate the original ink, adjust the drilling degree, mix the ink and then print, and check whether the printing plate and the ink roller are aging.
2. Viscosity is not stable. The ink is thixotropic, foaming, and the solvent is volatile. The ink should be stirred evenly and then added with an appropriate amount of defoamer (0.2%) to add a suitable amount of solvent to achieve a volatilization balance.
3. Poor drying. The imprint was not dry or even sticky in the expected time. The ink is highly drilled, and the poorly dried base paper or plastic and fabric are too poorly absorbed. Dilute the ink, adjust the printing pressure to increase the temperature of the blowing or drying tunnel, or use a quick-drying ink. Or adjust the dryness. Change the substrate to replace the shallow version.
4. The outline is blurred. The high-profile part of the printed image is blurred. The dot is faint and the tone is lost. The quality of the printing plate is not high. The printing plate and the ink roller are in too tight contact, the drilling degree of the ink is large, and the ink is coarse and the ink is dried too fast and the stirring is poor. The pad should be evenly adjusted to adjust the printing pressure. When adjusting the ink penetration, the water and alcohol should be mixed to properly stir the ink and adjust the ventilation device. Do not blow to the case, on the ink roller, and increase the speed of scrubbing with water containing monoethanolamine or adding 0.2% dimethicone or increasing the proportion of coupling agent.
5. The picture is crushed outside the ink extrusion image. The quality of the plate is too soft or the pad is too elastic. The contact pressure is too high. The ink is too low and the ink is too low. Pad the plate to adjust the height of the plate to adjust the printing pressure or manual screen printing blade pressure, adjust the drilling degree to change the ink with high drilling or change the ink with higher hardness and reasonably stir the ink.
6. Poor transfer. The printing pressure is insufficient, the hardness of the printing plate is too high, the water resistance of the paper is too strong, and the ink roller wears and deteriorates. Increasing the press pressure using a hydrophobic ink to check the wear of the ink roller wear aging adds TM-20. Coupling agent. Replace the metal anilox roll that blocks the wear.
7. It is difficult to overprint, and the multi-color overprinting sleeve is not allowed. The first color ink printing pressure is too large. The first color ink dries too quickly. The second color printing pressure should be increased, and the first color printing pressure should be light. Adding the right amount of TM-200S coupling agent The privacy of the first color ink should be reduced and the dryness of the first color ink should be adjusted or the second color should be printed when the ink film is not dry (overcoming the surface vitrification) The plate swells and bulges to replace the paper.
8. The ink is foamed, and the foam overflows after the ink is circulated in the ink fountain of the printer. The ink system foam suppressant has insufficient circulation of the ink, the water is too large, the pump circulation amount is too large, and the pipe leaking ink is too thin. Appropriate addition of defoamer (0.2% is best mixed with two plasticizing defoamers inside and outside) to reduce the pump circulation to replenish the new ink so that it does not excessively dilute the inspection tube to prevent air leakage.
9. Chemical pinholes. Adding anti-foaming agent in excess, the ink is diluted too much and the low-private ink is too inky. Note that about 0.2% of the defoaming agent is added. It should be mixed with the original ink and then re-printed.
10. The plate is worn. The contact is too tight, the overprint is too heavy, or the texture of the plate is too strong. Adjust the contact, adjust the printing pressure to replace the plate or pad 3mm plastic foam sheet on the back of the plate.
11. Ink gelation. A wrong solvent is used (some active molecules begin to associate to form a colloidal size aggregate). Mixed with other kinds of inks, improper storage, wrong colorants in the ink, the ink ages for a long time. Add about 2% silica gel or 0.3% TM-200 coupling agent with a solvent with good solubility, and seal and store the active adjuvant.
12. Paste sticking dirty / printing process sticking dirty and post-printing stack dirty. Friction occurs on the transfer rod and the film is peeled off to cause staining. The ink dry speed is too slow, the printing speed is too fast, and the ventilation heat is not too soft. Replace the harder ink and add a solvent that evaporates quickly (ethanol or acetone) to slow down the printing speed and increase the air volume.
13. Ink fading The color of the ink fades during printing or stacking. The ink system filler is too color-removing and the pigment is wrong (acidic and alkali-resistant). The carrier is too acidic. The ink pigment is not heat-resistant. Use fast-drying ink or less drier-dried ink. The pigment is made of heat-resistant and light-resistant stable pigment, and replaces the colorless calcium filler. Add inorganic mica powder or anti-ultraviolet absorber or antioxidant to 0.1% to 0.3%.
14. Striped orange peel. The print is not flat. The ink leveling property is too poor, the plasticizer is excessive, and the thixotropy is too large, sometimes the net has stains, the paper is not flat, the ink drilling is too large, the printing pressure is too thin, and the water is too large. Replace the thicker ink, reduce the printing pressure and change the water resistance of the good ink. Use opaque ink. Change the surface of the high-quality substrate to increase the filling amount (such as talcum powder can prevent sinking and improve leveling). Change the ink with a lower viscosity. Do not dilute the color to reduce the static electricity.
15. The blot is shed (pulverized). After the print is bound, moved or rubbed, the ink stains the prints and fingers. The ink is not properly adjusted to reduce the resin in the ink system or the solubility of the ink system solvent and the binder is unbalanced, but the wetness of the pigment filler is poor, the paper surface is too rough or the aluminum and plastic surface are too smooth. Increasing the resin content reduces the proportion of water as much as possible to balance the content with solubility.
16. Poor tolerance. Water resistant, light and abrasion resistant, and alkali resistant. Use the appropriate ink "The pH value of the strong ink film should be controlled between 7 and 7.5! Replace the light-resistant ink or add 0.2% anti-UV absorber or inorganic mica powder to use the softer ink.
17. Blocking the blockage of the net. The large f at both ends of the ink roll is like ink residue. The pigment system of the ink system is not neutralized by the alkaline binder and is neutralized and accumulated, and the paper is mixed with paper dust and plastic chip fabric. Reduce the printing pressure filter ink to adjust the ink. Use alkali-resistant pigments and alkaline active additives, and add the original ink with appropriate viscosity to the ink that has been printed for mediation.
Basic knowledge of ink storage and printing processes
1. After printing, the printing machine, ink roller and printing plate should be thoroughly washed. The waste water should be treated. The ink fountain should be sealed and sealed to prevent falling into the dust. Note that the ink will be separated immediately after the acid water and the iron barrel rust.
2. Ink should be kept in a cool place to prevent deterioration. Although it is water-based, it is prohibited to approach the fire source due to the presence of alcohol in the solvent to prevent the volatiles from being heated.
3. After opening the barrel (can box), it should be stored carefully. Do not bring in impurities, and use it with the open. Prevent the amine and ammonia of the ink system from being unstable after being volatilized. Light-transparent packaging drums (cans, boxes) are not available to prevent the intrusion of ultraviolet rays and cause instability in the oil.
4. If the gloss is not bright, it can be adjusted by adding tung oil or polymer resin plus acrylic resin or adding magnesium salt or TM coupling agent.
5. If the ink is too low, the fluidity is too low, the storage is easy to precipitate or the printing is easy to sag. An inexpensive aluminum salt or white carbon or bentonite may be added in an appropriate amount.
6. The dry speed of ink (such as 100-second dry embossing for 3-5 seconds) depends on the process of gravure, embossing and silk screen printing.
7. For water-soluble printing inks that are difficult to clean, add triethyl sulphate or TM-2005 coupling agent, and finally add inexpensive LLJ all-purpose solvent to improve ink rewetting or increase the amount of ink to reduce the ink ratio. The ink can be re-filtered due to coarse blocking of the textured ink roller. The ink stains when cleaning the printing press, cleaning the printing plate, cleaning the ink roller and cleaning the bucket tool are purified by filtration or introduced into the ground. Avoid its pollution to the environment.