Analysis of the Main Factors Influencing the Quality of Ink and Wash Color Printing(II)

Second, the practice of rotating packaging color printing

Around the problem of color printing, if alkali or ammonia or amine neutralizing agents are added too quickly or unscientificly in the process of preparing the ink, it is forgotten that the pigment is not only partially but gradually wetted and destroyed. The surface structure, when scratched or printed, the gloss of the ink film will be reduced, or even completely without gloss. At the same time, the addition of excess water molecules will also reduce its gloss. However, the fundamental difference between these two categories is that the former is a dark hue and fade of a color hue caused by the dripping of the pigment, dye, or acidified ink system in the ink system where strong alkali causes flocculation, while the latter is water. Excessive intrusion causes a rapid drop in viscosity (eg, high gloss viscosity is usually 45-60 seconds/coating—4 cups at 25° C., and when 17.5% water is added, the viscosity drops rapidly to 18-25 seconds/coating. - 4 cups (25°C matt or micro-gloss packaging printing ink film/250 g liner paper), resulting in a decrease in the solid resin content, resulting in a rich hue in the hue. Although from the surface, the polymer binder in a stable and curled state after adding water, when the external force acts to extend the segment structure until the molecules break, the printed ink film has no glossiness.

In another case, in order to reduce the cost of materials and completely use natural rosin with a molecular weight of only 330, in order to achieve the stability of the ink system space, in recent years, we have used dozens of inorganic materials that do not cause changes in chemical properties. The porous morphology of the tetrahedral hydrated silica acts as an associative colloid, making it capable of stably adsorbing on the surface of the low-molecular-weight rosin sol particles, forming a layer of a protective film, stretching the lyophilic groups into the water, both Can eliminate thixotropy, but also improve its water washability, and has a certain thickness, especially when more than 5%, the packaging printing ink film formed a short thick thick low molecular ink film, then more It will reduce the viscosity of the ink, thereby increasing the concentration, affecting both the fluidity of the printing transfer and the improvement of the gloss, which may increase the temperature of the ink system and reduce the association of rosin molecules in the process of associative heat release. tendency. In this regard, we selected the T-200S coupling agent (tackifier) ​​from Yizheng Tianyang Chemical Factory to improve the strength of the resin joints and increase the adhesive force of the glue solution to the adhesive surface, thereby effectively preventing the adhesive layer from being The peeling and peeling of the glued surface not only promotes the moist heat resistance of the glue in the ink system, but also increases the bond strength between the hard-to-stick material and the low-molecular-weight resin sol, the pigment and filler, and the gloss of the packaged ink film. And water washability. This is why the paint film is hard and the ink film is soft.

Table 2 Comparison of color ink color Red and yellow, printed with yellow, so you can add pink
Red color bright pink
Crimson darker than the red, slightly purple tendency
Light blue, red, dark and red
Pink, pale, purple, hue
The yellow color is slightly red and the hue is dark
Yellowish greenish, darker hue
Dark blue old, dark
Dark blue, not visible
Hole blue bright, vivid, yellow
Dark blue, bright color, with a small amount of light-colored red

Followed by the use of alkali-resistant pigments, dyes or fillers. Most of the dyes are used in light package inks that do not require light resistance.

Resins (whether natural or synthetic, be they macromolecules or low molecular resins) need to have dispersibility, transferability, fast drying, gloss, and abrasion resistance. At present, shellac and even acrylic resin have been replaced by pure rosin resin (to be tested before use). The method for preparing a resin liquid material with a conventional temperature-enhancing modification has been replaced by a method for preparing a rosin resin liquid material at room temperature. A green ink which is almost completely free from environmental pollution has been favored in the market.

Solvent, the traditional production of distilled water (ion water best), especially the need to add ethanol or isopropanol, but now the market mostly uses tap water or groundwater, in strict accordance with the PH index, trace addition is active, starting bridge and increasing Sticky TM-200S coupling agents have changed the production (process) method of making ink.

Third, the main subject of technical exchange

In addition to the above-mentioned success or failure of the discussion of exchanges, the following lists some of them that can be overcome, but it is easy to repeat the mistakes that have been made. This article tips out for everyone to discuss.

1. When remediating inks made from rosin resin, white ink or black ink made from alkaline binders and metastable titanium dioxide or carbon black often cause poor ink flow due to secondary neutralization of acid and alkali. Edition, forming a non-glossy packaging printing ink film.

2, the addition of cheap talcum powder, the ink is easy to hang and difficult to ink (and acrylic ink is the opposite).

3, the addition of a single defoamer overdose, the foam in the ink film can not avoid chemical pinhole before curing and drying. When the curing is dry, the printing ink film will cause the orange peel of the ridges. Although the filler is used to eliminate the orange peel, the hue of the remaining ink film is large.

4. Hydrated silica or magnesium salt as an associate, after the purpose of thickening and anti-settling, the ink film will still have a certain degree of gloss, and an excessive amount will be counterproductive.

5. Although the amount of chromogen or basic dye is small, the water can be washed, but it is not easy to wash after contacting the flexible letterpress and human skin.

6. Although inorganic pigments can overcome water washability, printing inks are prone to sedimentation or delamination, the ink layer is thickened, and dots are enlarged or lost.

7. Excessive dispersion of ink tends to exacerbate the swelling of the pigment fillers of the system. Aggregation and coarsening or coagulation are more difficult to control than formation of ink particle size aggregates by association with misuse of an active solvent molecule.

8. When the pigment filling that is not alkali-resistant is too high, the ink yield value is too high, and the filament becomes shorter. After the cheese-like ink is expanded, printing inks are printed and the color becomes lighter than the suction; the color of the packaging printing caused by the overdose, the clumping, and the disperse unevenness is more difficult for the operator to operate normally.

In short, in order to change the above-mentioned eight kinds of difficulties, we always try to use pigments and fillers with the same relative densities, but with unequal particle nucleus sizes, or to calculate the compatibility, or to use pigments with different relative densities but different particle sizes, Filler formula design will enable the flocculation, coalescence state to be eradicated. The main problems of green water-soluble water washable inks are: firstly, the control of PH value; second, the selection of materials and production process; third, the effect of ammonia, amine, and alkali addition order and speed, and fourth, the selection of neutralizer. The influence of type, content, and purity; Fifth, the thickness and whiteness of the substrate, and the influence of the pH value; Sixth, the performance and properties of the auxiliary agent and the effect of the thickness of the ink film layer; and Seven, the pressure of the packaging printing machine. The influence of co-solvents; 8 is the influence of contrast intensity and degree of harmonization when pigments, especially inorganic and organic contrasts (area, lightness, saturation) change; 9 is the workshop environment and temperature, humidity and printing machinery. Factors such as the influence of the cleanliness of the printing layout are worthy of our exploration and exchange.