Green packaging printing water-soluble inks have been printed on the surface of absorbent paper on webs for more than ten years. The use of modern technology will be domestically produced high-efficient additive additives and pure natural resin - rosin, direct composition and introduction of ink system, so that the ink used in flexible packaging plastic film, plastic woven bags, calcium plastic carton, leather and other materials printing, and in the non-absorption Printing on the surface of a material (plastic, aluminum foil, etc.) becomes a reality. Although it is slightly different from traditional ink manufacturing processes and technical indicators used at home and abroad, the principle of printing and packaging is the same.
First, green packaging ink
According to the composition of different color materials, auxiliary materials, fillers and auxiliary substances, there are two major categories of liquidity and paste ink with certain fluidity and fluidity. The application classification methods are as follows:
According to the printing plate type classification, there are flexible letterpress inks, gravure printing inks, and mesh printing inks and roll printing inks. According to the main components of ink classification, there are web and board printing inks, alcohol-soluble printing inks and water-based printing inks. According to ink use classification, there are paper printing ink, plastic ink and so on.
In short, pure green packaging printing ink is an industrial product for packaging products, which can be used for printing newspapers, magazines, food, packaging printing and decoration. Although paper, plastic, leather, etc. can be printed with green ink, due to the late start, there are many defects in the application method. To this end, the author is now based on the exploration of the past few years, I will master the use of essentials, fault prevention and solutions to the way or two, for packaging colleagues reference.
In the daily packaging and printing business, the green packaging ink is relatively thin, and most of them are also used in the operations of flexible rotary relief, rotogravure, rotary screen printing, and single-phase pneumatic diaphragm pump rotary water-soluble printing paperboard. In order to overcome the effects of ink layering and sedimentation in summer, winter ink jelly and thickening, which affect the normal packaging printing, we added a network structure to the ink components and can contain OH hydrophilic alcohol-based ions in the crystal lattice. The state of the inorganic and organic high-efficiency dispersion materials enhance the resistance to the destructive nature of the electrolyte and stabilize the ink. Although sometimes it is like other printing inks (layering or sedimentation, ink can be restored by agitating for only 1 to 3 minutes), due to many factors such as ink quality, printing materials, operating techniques, and so on, failures will occur. The indistinguishability will be indistinguishable, so it is summarized in the above-mentioned situations as failures, phenomena, causes and remedial measures. In order to prevent and adopt remedial measures for the packaging industry colleagues, we hope that the industry will improve feedback in a timely manner, break through the boundaries of the region and the system, improve the green packaging and printing ink formulations, process design, and dedicate their wisdom to create brilliant.
Second, the common ink failures and solutions
1. Blurred graphics. The printing ink layer is thin, and the ink and stroke are not clear; the ink is small, the ink is hard, the printing pressure is small, the ink's transfer rate and adhesion are poor (sometimes even in the layout, ink roller or intaglio pocket), black Ink is even difficult to manipulate in the printing process, and the surface of the printing material is rough. The solutions are: to adjust the amount of ink and viscoelasticity, adhesion fastness, improve the printing speed, reduce the printing pressure, increase the viscosity of the ink and add high-efficiency ultra-fine dispersion auxiliaries, to improve the ink transfer rate, adjust the printing pressure and select the smooth surface Materials, adjust the ink viscosity (painted 4 cups not less than 15s, the best is about 25s), improve the drying speed.
2. Crushing and smashing. Imprinting results in ink stains, large print pressures, poor layout flexibility, or deformation and unevenness of the press roll. The solution is: adjust the ink drying speed or reduce the amount of ink, reduce the pressure roller, change the flexo plate and correct the pressure roller.
3. Dirty and bite. The back of the print is dirty or overprinted by the previous ink, or the ink on the transfer belt of the impression roller is transferred to the next print; the ink is too sticky, the dryness is too slow, and the second color is easy to print. The first color is sticky; the surface of the conveyor belt is not clean or swollen, the printing pressure is too high, the machine speed is too fast, or the thickness of the printing material is not uniform on both sides or the winding tension is inconsistent. The solution is to increase the ink's initial dryness (rate), add a quick-drying solvent or oil, increase the proportion of lubricant in the ink (96:4), increase hot or cold blows, or slow down the printing speed And extend the printing stroke, select absorbable or surface roughened material, improve the surface absorption of the printing material, pay attention to the stacking of the printing material not too high and too heavy.
4. Ink splash. In the printing shop there are different sizes of ink dots or droplets. The ink has large yield value, large viscosity, ink layer thickness and ink film separation is too long or ink too thin, the printer speed is too fast, the ink viscosity is too small and does not anti-static, poor accuracy of the printer and ink roller deformation or surface Damage can cause ink splashing. The solution is: replace the ink roller (according to the ratio of the printing plate line and the anilox roller cable, choose 1:4 is appropriate), reduce the viscosity of the ink and reduce the drawing length and fluidity, reduce the ink supply, adjust the viscosity, and slow down Printing speed, adjust the temperature and humidity of the shop, replace the ink roller and repair equipment, or add antistatic facilities and materials.
5. Edition, ink roller sticky and scratches. The printing plate and the ink guide roller are stained by the ink on the printed material; the ink volume is too low and the viscosity is high, the ink contains impurities, the ink dries too quickly or too slowly, and the plated layer on the plate and roller wears, the hardness is not enough or The pattern is too deep, and dust such as paper and plastic increases. The solution is: replace the double-sided adhesive tape, adjust the pressure and adjust the blade and roller angle, reduce the amount of ink or replace the ink, increase the quick-drying solvent or oil, repair the version and roller, re-glazing chrome, prevent paper, plastic Such as powder dust off.
6. Poor adhesion and scratching. Printed products are easy to be wiped off. The surface of paper and plastic materials is too smooth and dense. It is not appropriate to use slow-drying inks. The ink resin content is too small and the surface treatment is poor. It cannot dry and float on the surface of printing materials in a short time. It is easy to wipe. Lost, commonly known as skin coke bones. The solution is: to improve the ink type, adjust the ink compatibility, handle the printing materials, use the ink with high viscosity and high ink concentration, increase the printing pressure, reduce the thickness of the ink film, reduce the printing speed, and adopt high-efficiency additives and viscosity-increasing inks. And change the solvent or oil that affects the speed of ink drying, exchange the varnish or thinner, and understand the suitability of the ink.
7. Residual irritating odor. The proportion of methanol in the ink is too large and is accompanied by odoriferous solvents or oils. The solution is: reduce the ink as much as possible or not use solvents or oils that are irritating or harmful to human health, exchange inks or replace solvents and oils.
8. Inaccurate shades and ink deposits. The color becomes lighter, discolored, and a paste plate is produced. The quality is inconsistent with the sample. The affinity of the color, the filler, and the linking material is poor; the storage is coagulated or severely stratified (thinning and thickening down) due to insufficient stirring before use. Solution: In the storage period, the ink should be stored in a cool, dry and ventilated place. The tone can be adjusted or exchanged to the value close to the hue of the sample. You can also add 1-3% of the white ink to the ink or increase the filler to increase the value. Covering power.
9. Pinhole and slippery. Chemical pinholes and mechanical pinholes appear in the printed pattern; spots occur in the entire plate, and ink overflows and foams during the printing process. When the viscosity of the ink is too low, the proportion of new ink or added resin should be exchanged to increase the viscosity, increase the flowability, and increase the printing speed. In the presence of foam, wetting and plasticizing defoamers should be added to eliminate foam, and the pattern depth should be changed to imprinting. Shallow, 25-30μm is appropriate.
10. Embedded version and orange peel. The ink has a large viscosity, many impurities, fast drying, unbalanced solubility, and ink is not level, resulting in the appearance of water marks and orange peels and ink residue and dry knots in the imprint pits, resulting in poor printing gloss, too light, and thixotropic Poor leveling, this is due to poor affinity between the printing plate and the paper, plastics, etc., auxiliaries discomfort, slow printing speed and electrostatic effects, then the printing speed should be adjusted to: high speed is 0.012 About s, the medium speed is about 0.055s, the low speed is O.09s, and the single sheet is 0.012s. (The time required for the ink to be transferred to the printing material); the angle of hot or cold air blowing is 90°, blowing or improving ventilation conditions, adding solvent, to achieve the solubility of solvents or oils and inks; changing the ink additives, reducing Static electricity and concentration of darkness as much as possible to achieve a gray balance.