Printing ink printing failure and processing method
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First, the whitening of the printing ink film
1-point whitening. The main reason is that the ink system is poor in the mutual solubility of the wax surfactants; the second is because the ink printing process is not reconstituted and the ink is transferred to the image.
Treatment method: An aromatic hydrocarbon or ester true solvent should be added to promote its dissolution. Or install a stirrer in the ink fountain (such as plastic tubing, put on the outside with unprinted plastic film, then tie the two ends tightly in the ink head to stir the ink randomly), or add anti-ink during the ink manufacturing Oxygen treatment.
2-point white point. The main cause is ink static or substrate static electricity. Or caused by the static electricity generated by the dilution solvent (the resistance is different due to different solvents). It usually occurs when the temperature is high or the printing speed is fast. Secondly, when the film is laminated, it is loose or loose before the front, and the static electricity is caused by the humidity.
Treatment method: increase the amount of antistatic agent in the ink (the excess affects the composite fastness), select the solvent with less resistance to dilute the ink, and adjust the grounding and receiving grounding wire (the general depth is 700 ~ 1500 mm).
3 crack type whitening. The main reason is that the ink transfer performance is too poor, and the second is that the pattern of the printing plate is too shallow and the solvent in the ink system is easily evaporated too quickly.
Generally, the roughness of the imprinting leads to poor film formation, especially the whitening of the ink system or the ink fountain diluent which is absorbed by the inhalation of water, and most of them occur in an environment where the humidity in the workshop is too high in summer.
Treatment method: replace the transferable ink or replace the deeper printing plate, and the third one is added to the slow dry solvent treatment.
4 whitening of the whole block. The main reason is that when the continuous printing time is too long, the operator repeatedly adds a single solvent when the viscosity of the ink becomes sticky or thick, thereby breaking the balance of the volatilization of the mixed solvent in the original ink system, resulting in printing ink. The ink layer is rough and white when filming. Second, even if the operator adds a mixed solvent, excessive addition tends to relatively reduce the content of the synthetic resin in the ink, and the above-mentioned whitening phenomenon also occurs. Treatment method: First, add 3% to 7% of slow-drying solvent, especially the true solvent that can plasticize the ink to resist the invasion of water molecules; the second is to use a special thinner containing resin; the third is to add 5 in the ink %~15% varnish to overcome whitening caused by insufficient resin content. Fourthly, install central air conditioner that can regulate temperature and humidity in the workshop or use a moisture absorber to eliminate it.
Second, the graphic brightness is insufficient (ie, the gloss is poor)
The whitening phenomenon listed above will be dull. Sometimes, although whitening is not achieved, the gloss of the ink film after printing is also affected.
Ink is thick and dull
Reason: Ink dispersion is excessively dispersed or mixed with paper or plastic chips and environmental dust during storage and printing; secondly, the diameter of the binder or pigment filler in the ink system is larger than 0.1 μm, resulting in insufficient brightness of the printed image, followed by the ink system. The resin content is small or the gloss is poor due to excessive addition of a dilution solvent (but not a true solvent) during printing.
Treatment method: After the ink reaches a certain fineness, it should not be ground again. It should be stored in a warehouse or workshop at room temperature of 15 ~ 30 °C. Second, improve the environment of the printing workshop to ensure clean and bright dust-free, and regularly remove paper or plastic chips; The third is to re-grind or filter the ink or replace the ink; the fourth is to add gold oil, true solvent or plasticizer in the ink fountain to reduce the viscosity of the ink.
Third, the imprint is fuzzy and trailing
The main reason is that the ink contains coarse and hard particles or is mixed with dust, paper dust, plastic chips and the like. The second is that the scraper has a slight defect and the tail is too thin, and the ink film is too soft.
Treatment method: one is to change the ink with high softening point or filter ink; the other is to clean the ink fountain or bucket mixed with dust, paper scraps or plastic chips; the third is to cover the ink in time, or install one on the ink bucket The top cover; the fourth is to replace the scraper or scraper blade with a piece of rubber or plastic foam sheet with a thickness of 1 to 3 mm to improve the ink scraping elasticity.
Fourth, graphic pinhole
The main reason is that the surface of the substrate is rough or the plate is stained; the second is that the active agent in the ink is too much or the ink is not matured (the foam does not disappear), which is often called chemical pinhole (different parts and different Area and different number of pinholes). In addition, the failure called mechanical pinholes is that the same part of the same substrate and the same size and number of pinholes are often repeated, rarely disappearing during the printing run-in period.
Treatment method: First, change the substrate (clean and smooth or unstained); second, control the amount of active agent in the ink system or add about 0.2% of defoaming plasticizer after 48 hours of ink storage (overfill will often cause ink film The shrinkage hole is difficult to level).
To solve the problem of pinhole failure of the mechanism: one is to change the printing plate or to open the printing machine after running for a period of time after the start of the printing machine, and the second is to adjust the printing pressure.
Five, the network point is lost or missing
Under normal circumstances, the cause of the failure is: first, the viscosity of the ink is too high; second, the ink film is dried too fast; third, there are particles in the ink; fourth, the ink leveling is too poor; fifth, the printing pressure is insufficient; The circumference of the plate sleeve is not flat, not smooth.
Treatment method: First, the viscosity of the ink should be adjusted between 25~30S/25°C and 4 cups; the second is to add slow-drying thinner to the printing; the third is to prevent the ink from drying out too early in the printing plate. (Adding a wetting aid); Fourth, adding 1% to 3% of flow-flat (such as ether) or adjusting the printing pressure, so that the substrate tension is controlled at 0.05; fifth is to change the printing plate or sanding Version surface.
Six, paste (in the non-text area)
The main reason for the paste is that the ink system has a low softening point or a low pH. Second, the viscosity of the ink is too high, the scraping blade is not clean, the hardness of the scraping blade is too strong and the toughness is insufficient or the blade angle is not right; the third is that the cold wind is insufficiently blown or the angle is not good when printing (the print will stick when it is serious); Rough and not smooth. Treatment method: First, it is better to change the ink reprinting with higher softening point or choose pH to be close to neutral; second, dilute the ink or pad a rubber behind the scraping blade (foam can also be used, its thickness should be 1~3mm The third is to adjust the angle of the cold air blower when the hot air blower (temperature should be based on the ambient temperature of 30 ° C or 35 ° C or 40 grades of three grades) (should be 25 °, 30 °, 35 °, 40, respectively) ° is good; the fourth is to change the plate.
Seven, printed adhesions
The reason is that the temperature is high and the printing speed is fast, so that the solvent in the ink film is not completely evaporated (relatively), or after the hot air blowing, the cold air blow is insufficient and not matured, and the ink is fast and slow. The volatilization rate is too high (resulting in wetness in the surface); the fourth is that the ink system invades the water molecules or is mixed with substances that promote oxidizing properties (such as metal lead, cobalt, manganese salts), so that the printed ink layer is stored during storage. Gradual oxidation (release) caused by stickiness.
In addition, when the ink enters the factory, it is stored in a poorly ventilated warehouse, especially if the softening point of the binder is low or the anti-stick anti-skid component is too little ink, and secondly, the pattern of the gravure plate is too deep and the printed ink film is thick after transfer. Back sticky. Treatment method: In the season of gas temperature, the printing speed should be slowed down as much as possible or anti-adhesive additives should be added to the ink; the second is to use fast, medium and slow mixed solvents and use as little solvent as possible to adjust the ink; After blowing, increase the cold air blowing or adjust the blowing angle; the fourth is to measure the ink film that is completely dry, and re-adjust the printing machinery speed according to its drying time; cover the ink fountain or barrel or cover the ink at any time to prevent water molecules. Metal salts that invade and prevent oxidizing properties; Fifth, the ink is stored in a ventilated and dry, non-humid low temperature warehouse; and the sixth is to re-plate (the plate depth is between 25 and 45 cm, and the printing ink with higher softening point is replaced.
Eight, the ink film is crystallized and it is difficult to overprint
Generally speaking, it is difficult to print the second or third color ink after the film formation of the previous ink, and the surface has formed crystallization (ie, vitrification)/mainly because the properties of the two inks are different or different in composition. Re-solubility (ie, poor affinity) is poor; second, excessive silicon lubricant is added to the ink system, especially in hot weather operation; third, the surface of the composite ink lacks matt or anti-stick which can form a rough surface after film formation. The antistatic agent causes the surface to be too smooth; the fourth is that the printing plate hole (pattern depth) is too shallow or the ink fluidity is too large or the viscosity is high.
Treatment method: increase the amount of true solvent in the ink system to increase its resolubilization affinity, and replace the ink with the same color (the same nature brand and manufacturer); the second is to use the ink containing silicon lubricant as much as possible. One color, the second or third ink is printed when slightly viscous. Add appropriate amount of matt powder in the composite ink (without affecting the surface gloss as standard) or subtract the anti-sticking and antistatic dose, change the printing plate or re-create the graphic printing plate of 25~45 μm depth, or use the content High, low-viscosity, but highly rollable inks regularly eliminate plate ink sticks.
Nine, poor composite fastness
The printing composite is not strong, mostly due to the ink system or the printing process is diluted, the resin content in the ink system is too small or the viscosity of the ink is too large, and there is also a detachment caused by the special ink and the composite adhesive. On the other hand, the difference in surface tension between the ink and the substrate is too large and the composite is not matured (cooled) after printing, or the solvent is completely evaporated and the ink hardness is too small (the film is too brittle, too thick / the fingerprint is too deep) ). In particular, the printing material is not treated well, and the printing pressure is small and the imperfections and tearing phenomenon appear. Note: The control of surface tension is mainly for the corona discharge treatment of the printing material.
Treatment method: using a printing composite ink with high resin content but small viscosity, according to the type of ink provided by the ink factory, the ink and adhesive of the same nature as the printing material are selected; the second is to adjust the surface tension controller of the printing machine (making it In the range of 38dyn/cm2, due to the different initial or dry time of different solvent-based inks, the adhesion fastness should be re-examined after 48h ripening (for example, the dry speed and adhesion are not due to viscosity, When using 175-line printing layer printing, the technical parameters are: white ink / viscosity 25 ~ 30S / 25 ° C · coating 4 cups (40 ~ 100 m / min printing speed); and color ink viscosity should be controlled at 28 ~ 33S / 25 °C·coating 4 cups (100-140m/min printing speed) range, while the actual application is lower than average 5
S or so. The fifth is the printing of the film in a short time, and the viscosity of the diluted ink is lower.
S or around the use of fast-drying solvent, slow-drying solvent supplement, to promote the close combination of dissolved hydrogen bonding force. Seventh is to change the printing roller with a depth of between 15 and 35 μm. Eighth, if the ink appears in the shape of water, it should be temporarily added with gold oil or special thinner. It is best to use the thinner specially produced by the ink factory, or TM3. Nine is designed according to the "two-dimensional method" to mix thinners to avoid poor adhesion.
Ten, not resistant to cooking or smell
After printing and compounding, the packaging is not resistant to cooking, and most of the amide resin that has been permeabilized (dyed) or softened at the time of disinfection will cause blurring, fading, fading, or residual solvent odor. Slowly inward or outward. This phenomenon is generally caused by the fact that the ink itself is not heat-resistant, and the heat and pressure are too large. The odor is caused by the addition of methyl ethyl ketone or toluene solvent during the printing process, or the use of polyisocyanate compound glue. Although the printing and compounding process is finished after hot air and cold air blowing, the free cyano group remaining in the rubber compound during the secondary or tertiary disinfection process of the packaging will inevitably be generated again. The same reason. If the above materials are used, the fault will repeat itself. Because the printing compound is compounded for a moment, it is difficult to completely evaporate the solvent, and the ink film and the rubber compound are dry. Especially in the case that the detection and control equipment is not perfect, small packaging printing manufacturers are more difficult to solve.
To this end, the following treatments are recommended:
1. The solvent or adhesive should be added as little or as little as possible in the ink.
2. Increase the hot air blower and the cold air blower, especially after drying out and then laminating.
3. The ink should be diluted with fast-drying solvent or extruded.
4. Change the ink type of heat-resistant pigments. When making ink, choose a small acid value, resin or light-resistant transparent dye, use non-azo type pigments and dyes to avoid the production of poisoning or carcinogens, or add 1% ink factory. Fixative.
5. During the printing process, a cover can be added to the ink fountain to dye the water-proof molecules (especially the intrusion dyeing of acidic substances).
6. Control the volatile residue of different solvents.
Eleven, dirty version (or called print with dirty)
The dirty version of the ink is almost the same as the dirty version of the printed ink. The reason is:
1. The 1st version of the roller is chrome-plated rough which is the most common cause of failure;
2. There is a thin layer of ink on the non-printing surface (sometimes there are different regular strips); the ink has strong wettability on the chrome surface, causing the scraper to be scratched;
3. scraper is too pure or the angle is wrong;
4. The ink is too dry at the beginning or the silk is too long.
Approach:
1. If the chrome surface of the new roller is rough, a quick-drying solvent can be used in the ink to dry the thin ink layer formed between the blade and the embossing roller. After a few hours, the chrome surface is ground and replaced with a normal solvent. ;
2. switch to a new scraper and adjust its angle;
3. Solubilizer, especially to accelerate the dry solvent to reduce the viscosity of the ink - such as the smear or gold oil; 4 is to add the slurry of calcium to reduce its silk to increase the thickness and fluidity of the ink layer of the printing ink.