In the packaging printing production process, operators often encounter one or more failures caused by ink quality problems. For this reason, this article puts forward its own opinions on some problems.
1. Composite inks have no problem in printing, but there are white spots in the composite aluminum plating film, and the hiding power is also greatly reduced. How to deal with the above problems?
First, increase the amount of colorant in the ink; secondly, introduce the alcohol ether solvent or add a leveling agent when designing the formulation; thirdly, increase the amount of antistatic dispersant or auxiliary resin with low viscosity; Fourthly, during the printing, the blade is moved upwards or the printing pressure is increased appropriately. The printing plate of the deep hole can also be replaced to increase the thickness of the ink film and promote the wetting and leveling of the ink.
2. Table printing ink is not inked during printing. How to deal with it?
The ink is not adhered to the substrate, indicating that the formula design of the ink is unreasonable. For example, when several mixed solvents are used together, the surface is likely to form oil beads. This indicates that there is no mutual solubility between the solvents, or the resin in the dissolving ink system is not reached. The solubility. The second is that the thickening of the ink in the ink system is caused by thickening or gelation of the ink. In severe cases, the ink piles at both ends of the plate, and the ink is not transferred or the transfer rate is insufficient.
Before the ink production, first, design the formula according to the two-dimensional ink making method as much as possible; second, minimize the amount of thickening thixotropic agent; third, add the solvent for dissolution when printing; fourth, avoid the stupid touch of ink and water; It is the exchange of new ink.
3. What is the color ink toner?
In short, resin plus pigments are mixed, milled or filtered. The former is a color film, and the latter is a toner. Producers can choose different pigments for printing applications, especially resins in color chips or toner systems
4. How does gravure plastic ink, especially white ink, prevent yellowing and increase whiteness?
According to different gravure plastic inks, different formulas should be used, such as polyurethane ink or universal surface printing or universal ink printing. The method used is different. Polyurethane gravure ink systems often contain toluene or xylene. After printing, the graphic ink film contacts the oxygen in the air and yellowish. In particular, the ink composition using anatase titanium dioxide is more yellow.
In order to avoid the above-mentioned failures, one is to use urethane resin-free urethane resin as the binder for the ink system; the other is to change from anatase to rutile. The easiest way is to add 0.01% to 0.03% brightener or 3% to 5% TS colorant, which can not only greatly improve the whiteness, but also can significantly reduce the ink cost.
5. PP woven bag flexo ink, especially black ink how to improve the attachment fastness?
The ink system is generally dominated by alcohol-soluble polyamide resins. In order to improve the adhesion of ink, one is to introduce the crosslinker or wetting dispersant or slow-drying solvent in the ink system; the other is to add the aldehyde-ketone resin; thirdly, to adjust the surface tension of the ink and the PP as much as possible during the ink formulation design. Surface tension design is close to some as well. As for the proportion of resin in the black ink can be a bit larger or added to the TU-3100, if the printing pressure is properly increased, it is also feasible.
6. After the white ink is exposed for 1-2 hours, it first turns from white to yellow, and then the color gradually fades away. How can this problem be explained and handled?
The yellowing of white can be seen in point 4 of this article. However, yellow gradually faded into five colors, mainly related to titanium dioxide. Because anatase titanium dioxide itself is acidic, plus some ink manufacturers do not ask the ink category, all adding brighteners, which not only accelerate the process of yellowing, but also because of the use of non-optimized brighteners have played an oxidant Effect, which led to the emergence of the above failures.
In order to overcome this kind of trouble, in the ink system, the anti-UV absorber or mica powder can also be changed to rutile type white powder to prevent future troubles.
7. How to increase the gloss of PP woven bag ink?
The first proposal is to increase the resin content, the second is to add leveling additives, the third is to add the boiling point in the ink system at 150 ~ C-245 °C solvent 2% -5%, the fourth is to add the polyketone or 3% -5 Damar resin %, the fifth is to extend the grinding time of the ink or add about 3% of erucic amide as a flexible filming aid for the ink, so as to promote the increase of gloss through the diffusion and flow of macromolecules. The proper crystallinity of the ink improves the cohesion and adhesion of the printing ink.
8. When thermoplastic PU resin is used, the glossiness of the produced black and black ink drops and the coloring power deteriorates. What causes this and how is it handled?
In the PU resin ink system, the above phenomenon is often caused by the failure of a single solvent to fully achieve the solubility of the PU resin. When we add a cosolvent solvent or a coupling dispersant, its solubility is close, the transparency is good, and the coloration of the ink is improved. Of course, there is a poor pigment dispersibility or a short polishing time, and the thick ink is the cause of the above phenomenon. This not only reduces the gloss of the ink film, but also the ink is not as bright as the coloring power. For this purpose, we recommend the use of TM-27 or Bu18A dispersants, which can also extend the grinding time, add additional solvents (for example, toluene can be mainly butanone, and isopropyl alcohol can be mainly n-butanol) or slow-drying. Solvents can increase the gloss of printed ink film.
9. After CPP resin and toluene solvent are used to make ink, the ink is stored for a period of time, and CPP tends to precipitate on the surface. If it is in winter, it will be noticeable. Why?
The reason why the above trouble occurs after the ink is produced by the solution of the CPP resin plus the toluene solvent is that the solubility between the CPP resin and the toluene is about 10%. Since CPP and toluene are dissolved under certain temperature conditions or under certain shearing conditions, the instability of 2PP (precipitation) is common due to the difference in solubility. The Canadian CPP. The level of chlorine will also bring about the above problems. For this reason, it is recommended to add some butanone or ethyl ester as the auxiliary solvent is often very effective. Adding alcohol ether ester solvent can increase CPP. The water resistance, but also can make CPP and toluene immiscible, to achieve the reduction of solvent ink graphic film ink residue.
10. How to reduce the ink material cost?
(1) Reducing the resin content, or reducing the resin with high price and low supplemental price is an auxiliary resin.
(2) Adding a low-cost RT 3%-5%, reducing the high-price pigment 2%-4%, or force D. People TM - 27 to reduce L 18A or 1220.
(3) Increase thickening thixotrope to reduce the effect of tree moon and pigment.
(4) When designing ink formulations, ink formulations with similar solubility of resin and solvent, similar hydrogen bond strength, similar surface tension, and similar volatilization velocity should be considered. Generally, 30% to 50% of the dilution solvent is added without affecting -n Ink quality and ink formulation. For example, the principle of inorganic binder: acid, alkali, similar structure, ion radius. The ratio is similar to the number of compatibility.
Because the binder in the ink is a liquid dispersion medium, it is a carrier for pigments and fillers, it has a certain viscosity and fluidity, film formation, can effectively disperse pigments and fillers, and gives ink flow. Ability, printing ability and film forming ability
Author/Liu Jiaju