Linyin ink printing failure and its treatment

1. Whitening of printing ink film

â‘  Point-type albino. The main reason is that the ink system has poor mutual solubility for the wax surfactants; the second reason is that the printing process is not reconstituted after the ink is skinned and is transferred to the graphic.

Treatment method: Aromatic hydrocarbons or ester real solvents should be added to promote their dissolution again. Or install a stirrer in the ink fountain (if using plastic pipes, use an unprinted plastic film on the outside, and then put the two ends tightly in the ink head and rotate randomly to mix the ink), or add resistance during ink manufacturing Oxygen treatment.

â‘¡ Dotted white dots. The main reason is caused by static electricity of ink or static electricity of printing material. Or due to the static electricity generated by the diluted solvent (the resistance of different solvents is also different). It usually occurs when the temperature is high or the printing speed is fast. Secondly, when laminating the film, it should be tight before loosening or loosening tight before loosening, and the static electricity is usually caused by high humidity weather.

Treatment method: The antistatic agent can be increased in the ink in an appropriate amount (excess will affect the compound fastness), select a solvent with a smaller resistance to dilute the ink, adjust the placement and reception of the grounding wire (generally 700 to 1500 mm in depth).

â‘¢ Crack whitening. The main reason is that the ink transfer performance is too poor, and the second is that the plate pattern is too shallow and it is easy to make the solvent in the ink system volatilize too quickly.

Generally, rough imprints lead to poor film formation, especially the whitening that occurs when the ink system or ink fountain thinner is added to absorb water, and most of them appear in the environment where the humidity in the workshop is too high in summer.

Treatment method: replace the ink with good transferability or replace the deeper printing plate, and add the slow-drying solvent for treatment.

â‘£Albino of the whole print. The main reason is that the continuous printing time is too long. When the operator finds that the viscosity of the ink becomes sticky or thick, he repeatedly adds a single solvent to break the balance of the volatility of the mixed solvent in the original ink system, resulting in printing ink. The ink layer is rough and white when the film is formed. The second is that even if the operator adds a mixed solvent, the excessive addition will often reduce the content of synthetic resin in the ink, and the above-mentioned whitening phenomenon will also appear. Treatment methods: one is to add 3% to 7% slow-drying solvent, especially a true solvent that can plasticize the ink and resist the invasion of water molecules; the second is to select a special thinner containing resin; the third is to add 5 to the ink % To 15% of ink-adjusting oil to overcome the whitening caused by insufficient resin content. Fourth, install a central air conditioner that can regulate temperature and humidity in the workshop or eliminate it with a moisture absorber.

Second, the brightness of the graphic is insufficient (that is, the gloss is poor)

The whitening phenomenon listed above will be dull. Sometimes, although it does not reach whitening, it also affects the gloss of the ink film after printing.

The ink is thick and matt

Reasons: Excessive grinding and dispersion of ink or storage, mixing of paper or plastic scraps and environmental dust during printing; Second, the diameter of the binder or pigment filler in the ink system is greater than 0.1μm, which leads to insufficient brightness of the printed graphics, followed by the ink system Poor gloss caused by low resin content or excessive dilution solvent (but not true solvent) added during printing.

Treatment method: The ink should not be ground again when it reaches a certain fineness, and should be stored in a warehouse or workshop at 15 to 30 ℃ room temperature. The second is to improve the environment of the printing workshop to ensure that it is clean and bright without dust, and regularly remove paper or plastic debris at a fixed point; The third is to re-grind or filter the ink or replace it with new ink; the fourth is to add gold oil, real solvent or plasticizer to the ink fountain to reduce the viscosity of the ink.

3. The imprint is blurred and trailing

The main reason is that the ink contains coarse and hard particles or is mixed with dust, paper scraps, plastic scraps, etc. The second is the trailing tail caused by a slight defect of the scraper, and the ink film is too soft.

Treatment method: First, replace the ink or filter ink with high softening point; Second, clean the ink fountain or bucket mixed with dust, paper or plastic scraps; Third, cover the ink in time after use, or install one on the fountain bucket Top cover; Fourth, replace the scraper or scraper blade and add a piece of rubber or plastic foam sheet with a thickness of 1 to 3 mm to improve its scraping elasticity.

4. Graphic pinhole

The main reason is that the surface of the substrate is rough and uneven or the printing plate is stained; second, there is too much active agent in the ink or the ink is not mature (the foam has not disappeared) completely, often called chemical pinholes (different parts and different Area and different number of pinholes). In addition, the failure known as mechanical pinholes is that pinholes in the same part of the same substrate and the same size, area and number are often repeated, and rarely disappear during the running-in period of printing.

Treatment methods: First, replace the substrate (smooth and smooth or not stained); Second, control the amount of active agent in the ink system or add about 0.2% of defoaming plasticizer in the ink storage for 48h (overdose will often cause ink film Cratering and difficult to level).

The method of solving the pinhole failure of the mechanism: one is to change the printing plate or start the printing machine and start running after a period of time before printing, and the other is to adjust the printing pressure.

5. Loss or defect of outlets

Under normal circumstances, the cause of this failure is: first, the viscosity of the ink is too high; second, the ink film drying is too fast; third, there are particles in the ink; fourth, the ink leveling is too poor; fifth, the printing pressure is insufficient; sixth, The circumference of the printing plate sleeve is uneven and not smooth.

Treatment methods: First, the viscosity of the ink should be adjusted between 25 ~ 30S / 25 ℃ · 4 cups; Second, the ink should be added with a slow-drying thinner during printing; Third, the ink should be prevented from premature drying in the plate cavity (Add wetting aid); Fourth, add 1% ~ 3% leveling (such as ethers) or adjust the printing pressure, so that the tensile force of the substrate is controlled at 0.05; the fifth is to change the printing plate or polish the printing Edition surface.

Six, paste version (in the non-graphic area)

The main reason for the paste version is: the ink system has a low softening point or a low pH value. The second is that the viscosity of the ink is too high, the scraper is not clean, the hardness of the scraper blade is too strong and the toughness is insufficient, or the angle of the scraper is wrong; third is that the cold wind is not blown enough or the angle is not good when printing (it will make the printed matter sticky when it is serious); Rough and not smooth. Treatment method: First, replace the ink with a higher softening point for reprinting or choose a pH value close to neutral; second, dilute the ink or add a rubber on the back of the blade (foam plastic is also available, its thickness should be 1 ~ 3mm) ); The third is to adjust the angle of the cold air blower (the temperature should be 25 °, 30 °, 35 °, 40, respectively) after the hot air blower (the temperature should be based on three levels ranging from 30 ℃ or 35 ℃ or 40). ° is good; the fourth is to change the printing plate.

Seven, printed product adhesion

The first 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 speaking), or after the hot blowing, the cold blowing is insufficient and the drying is not mature, there are also some The volatilization rate is too large (resulting in surface dry and internal humidity); Fourth, the ink system has invaded water molecules or mixed with substances that have oxidizing properties (such as metal lead, cobalt, and manganese salts), so that the ink layer is stored during printing 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 link material has a low softening point or the anti-slip anti-slip agent component has too little ink, followed by the gravure printing plate is too deep and the printing ink film thickness appears after transfer Stick back. Treatment method: In the season of air temperature, the printing speed should be adjusted as slow as possible or anti-sticking additives should be added to the ink; the second is to use fast, medium and slow mixed solvents and as little as possible to adjust the ink with real solvents; the third is to heat After blowing, increase the cold blowing or adjust the blowing angle; the fourth is to measure its thoroughly dried ink film, and readjust the printing machine speed according to its drying time; add ink to the ink fountain or bucket or cover the ink at any time to prevent the water molecules Metal salts that invade and prevent oxidation; Fifth, store the ink in a ventilated, dry and low-temperature warehouse with no humidity; Sixth, remake the plate (plate depth is between 25 and 45 cm, and replace the printing ink with a higher softening point).

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Eight, the ink film is crystallized and it is difficult to overprint

The general performance is: it is difficult to print the second or third color ink after the previous ink is filmed, and the surface has formed crystallization (ie, vitrification) / mainly because the two inks have different properties or different components , Poor resolubility (that is, poor affinity); Second, too much silicon lubricant is added to the ink system, especially in hot days; Third, the surface of the composite ink after film formation lacks a matte or anti-sticky surface that can form a micro-rough surface 1. Antistatic agent causes the surface to be too smooth; Fourth, it is caused by too shallow plate cavity (pattern depth) or too much ink fluidity or high viscosity.

Treatment method: increase the amount of true solvent in the ink system to increase its reconstitution affinity, replace the ink with the same color as the previous color (brands and manufacturers of the same nature); second, choose the ink containing silicon lubricant as possible One color, the second or third ink is printed when it is slightly sticky. Add appropriate amount of matt powder to the composite ink (without affecting its surface gloss) or subtract the anti-sticking and anti-static doses, replace the printing plate or remake the graphic plate with a depth of 25-45 μm, and the content can also be selected. Ink with high viscosity and low viscosity, but with high rolling performance, regularly eliminates plate ink sticking.

Nine, poor compound fastness

The Indian-Indian composite is not strong, mostly due to the ink system or the dilution of the printing process, the resin content in the ink system is too small or the ink viscosity is too large, and there are also unselected detachments caused by special inks and composite adhesives. On the other hand, the gap between the surface tension of the ink and the substrate is too large, and the compound is not matured (cooled) after printing, or the solvent is completely evaporated without drying and the ink hardness is too small (the film is too brittle, too thick / this index is too deep ). In particular, the printing materials are not processed well, and the printing pressure is small and the phenomenon of intolerable rubbing and being torn off occurs. Note: The control of the surface tension is mainly for the corona discharge treatment of the printing material.

Processing method: Use printing compound ink with high resin content and low viscosity, and select ink and adhesive with the same nature as the printing material according to the variety and model provided by the ink factory; Second, adjust the surface tension controller of the printing machine (make it in In the 38dyn / cm2 range, due to the different initial or through-drying time of different solvent-based inks, the adhesion fastness should be re-examined after 48h of aging (for example, due to viscosity, the drying speed and poor adhesion, in When using 175-line printing gradation printing, the technical parameters are: white ink / viscosity 25 ~ 30S / 25 ℃ · coating 4 cups (40 ~ 100 m / min printing speed); and color ink viscosity should be controlled at 28 ~ 33S / 25 ℃ · Coating 4 cups (100 ~ 140m / min printing speed) range. The actual application is about 5 S lower. The fifth is the printed matter with short time laminating, the viscosity of the diluted ink is about 3 S lower or quick drying The solvent is the main, and the slow-drying solvent is the auxiliary, which promotes the close combination of the hydrogen bonding force. Seven is to replace the printing roller with a depth between 15 and 35 μm. Eight is If the ink appears water streaks, you should temporarily add gold oil or special thinner. It is best to use the thinner specially produced by the ink factory, or TM3. Nine is to design and mix the thinner according to the "two-dimensional method" to avoid adhesion bad.

Ten, intolerant to cooking or smell

After printing and compounding, the packaging is not resistant to cooking. Most of the imprinted (stained) or migrating amide resins with lower softening point after disinfection cause blurry graphics, faintness, fading, or residual solvent odor. This phenomenon is generally due to the slow inward or outward escaping because the ink itself is not heat-resistant, which is more obvious after the heat and pressure are too large. Odor is caused by the addition of methyl ethyl ketone or toluene solvent in the printing process, or the use of polyisocyanate compound glue. Although the composite printing process is ended after being blown by hot air and cold air, the free cyano group remaining in the rubber compound during the second and third sterilization process of the package will inevitably be generated again. Empathy. If the above materials are used, the fault will be repeated. Because it is difficult to completely evaporate the solvent and dry the ink film and glue at the moment when the printing compound is compounded. Especially under the condition that the detection and control instruments are not perfect, it is more difficult for small packaging and printing manufacturers to solve.

To this end, it is recommended to adopt the following treatment methods:

â‘  The above solvents or adhesives should be added as little as possible or not in the ink.

â‘¡Increase hot and cold air blowing, especially to remove the film after drying.

â‘¢The ink should be based on quick-drying solvent or extruded compound when diluted.

â‘£Replace the ink types of heat-resistant pigments. When making inks, choose dyes with low acid value, resins or light-resistant transparent dyes, non-azo pigments and dyes to avoid the occurrence of poisoning or carcinogens, or add 1% of ink factory production Fixative.

⑤ A cover can be added to the ink fountain during the printing process to stain with waterproof molecules (especially the intrusive dyeing of acidic substances).

â‘¥ Control the volatile residue of different solvents.

Eleven, dirty version (or called printed with dirty)

The dirty version of the Indian ink is almost the same as the dirty version of the surface printing ink. The reason is:

â‘ The chrome plating of the roller is rough. This is the most common cause of failure;

â‘¡ There is a thin layer of ink on the non-printed surface (sometimes there are different regular strips); the ink has a strong wettability on the chrome surface, causing the scraper to scrape;

â‘¢The scraper is late or the angle is wrong;

â‘£Ink drying is too slow or the filament head is too long.

Approach:

â‘ If the chrome-plated surface of the new version of the roller is rough, you can use a quick-drying solvent in the ink to dry the thin ink layer formed between the doctor blade and the impression roller. After a few hours, after the chrome surface is ground, the normal solvent should be changed. ;

â‘¡ Change to a new scraper and adjust its angle;

â‘¢ Add solvent, especially to accelerate the dry solvent to reduce the viscosity of the ink-such as desalting agent or gold oil; â‘£ is to add slurry calcium to reduce its silk head and increase the ink layer thickness and fluidity of the printing ink.

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