Understanding the water-based ink system
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Almost no printing can be as rapid as the current Flexo printing. In a very short period of time, it was only a "package" printing from people's impressions, which evolved the reproduction of high-quality photoengraving. In such a short period of time to achieve such an overall development, it is difficult to use the general assessment to be the industry or the supplier's credit, of course, these advances are not just to the ink supplier.
Flexo printing is not a single job. Today we have pre-pring and post-printing for old slow-moving machines and new high-speed machines for corrugated boxes; wide- and narrow-spoke plastics for flexible packaging. Film Flexo printing; paper printing including facial tissue and napkins; and many different prints, narrow-spoke Flexo printing such as labels, tickets, coupons and the latest developments in Flexo UV carton printing.
In addition, we have a variety of different water-based inks and solvent-based inks, we can choose a variety of inks and ink systems. Printing ink is not retained regardless of raw materials or formula
Secret or surprise, is not to trust a certain practice or must use some kind of practice to achieve high quality.
Today I want to browse some recipes about water-based inks. What is the ink? What are the ingredients? What effect will it have? Of course, such a short space is difficult to cover all the details, so I only give you a little idea.
What is printing ink?
It is a chemical mixture. The water-based inks referred to by Flexo printing are low-viscosity, and their viscosity is measured by a standard measuring cup.
Class=”amai”>What is water-based ink?
Water-based inks are a combination of four different chemical materials, which are:
Coloring material - it is a visual sense that allows us to see the color.
Resin - it will transfer color to the surface of the body.
Additives - It is a combination of some raw materials to correct the performance of the ink.
Solvent - It reduces viscosity and makes it easier to transfer ink to the print and then dry.
Of course, the solvent for aqueous inks must be water, but some suppliers still mix some flammable solvents, also known as water-based inks.
For nowadays, the main function of the ink is to present a message or to show a selling point. It is often a perfect picture, so the most important part of the ink is the color. The colorant is one of the dyes or pigments. The dye is a general coloring agent and can be found in food additive colors and pen inks. Although the printing effect is not good and it is easy to fade, some paper printing and cardboard printing are still in use because of the low price.
Today's high-quality inks are chemically synthesized using pigments, with the exception of the well-known carbon blacks and large amounts of dioxide. In fact, the appearance of the pigment and its properties come from the resin that carries it. Formulated with more than 100 pigments to cover the spectrum of all colors.
However, in normal use, the typical ink formulation is limited to about 50. Several color pigment manufacturing plants in the world include BASF in Germany and some small factories. The color material manufacturing is batch, but the color of each factory is slightly different. There are four colors of ink in general: blue, magenta, yellow, and black. Each set has a little difference, and there is no real standard. In particular, the colors that the Eastern and Western markets pay attention to are different. For example, the red ink is the blue color of the East and the yellow color of the West.
Pigments are an expensive component in inks that increase cost by requiring higher resistance and higher color strength. The choice of the print also affects the choice of color. For example, in a special case, we are required to make a blue ink that will be printed on white cardboard, but the yellow cardboard is used for proofing.
Another part of the ink formulation is the resin or load transfer system. The main function of the resin here is to transfer the pigment from the printing process to the substrate. The first step of these processes is to dissolve the resin in the solvent through the printing plate onto the print, and after the solvent is absorbed or evaporated to dry, the resin is left to carry the color. We have a lot of resins to choose from, and it is impossible to use only one resin. Maybe we will consider the requirements of the printed matter with different resins, such as: high temperature resistance, acid resistance, high gloss...
Typical resins for aqueous inks are:
Prevent water from diffusing particulate resin.
A resin that does not dissolve in water.
A resin dissolved in hydrophobic water.
The third element of ink composition is “water”. Its main function is to make the ink more fluid, so that the ink can be carried from the engraved ink tank of the pattern roller to the body, when the resin and pigment are brought to the print. In the case of body, the water must be removed, which is difficult on the non-absorbent film, so the removal rate and drying speed are very important in the printing process.
The water in the ink is limited to organic solvents because it affects the drying speed of the water and reduces the solvency. The water in the ink is not too stagnation, and the pH, hardness, and softness of the water affect the dryness. Soon we talked about the pH of the water.
Additives are the least formulated in aqueous inks, and their addition is the most visible or corrected ink performance. There are also many types of additives, and we must choose their function and be able to fully integrate with the ink components. Additives include surface smoothing agents, defoamers, leveling agents, synthetic resins, and the like.
Let's talk about the use of certain raw materials, such as heavy metals, chemical solvents, synthetic resins, etc., which will cause environmental problems. I remember that some suppliers mentioned before, and did not restrict the use of such materials according to standards. There are still many problems in the Asian region. Although the government's laws and regulations are not strictly regulated, you should consider exporting.
A typical printing ink composition would be:
Solvent 70%
Color 10%
Additive 5%
Resin 15%
Of course, this is only a rough value, and the final decision must be made based on the requirements of ink and print quality. Nowadays, for high-quality Flexo printing, the color component can be added to 17%, which means that we can consider the need to adjust the composition ratio. The most important thing for a printer is to achieve a satisfactory quality at an acceptable cost; and to have both environmental and health issues.
The basic concept of ink printing is already there, but I want to declare that this is the simplest version. Let's go back to the viscosity problem. Every element we talked about earlier will affect the viscosity.
Often the ink merchant will ask you what viscosity you need, or what viscosity you recommend. However, ink viscosity is important, whether it is a job to another job, or a press to another press, or other conditions may have different viscosities. It depends on several aspects, different printing models, inked rollers, scrapers or different pattern rollers and mesh thickness. Often the ink merchant will ask you what viscosity you need, or what viscosity you recommend. However, ink viscosity is important, whether it is a job to another job, or a press to another press, or other conditions may have different viscosities. It depends on several aspects, different printing models, inked rollers, scrapers or different pattern rollers and mesh thickness. Viscosity is easily measured in the measuring cup, but care must be taken to ensure temperature changes and the cleaning and protection of the measuring cup.
In terms of drying, water evaporation is an important factor, especially on non-absorbent materials, which can use an energy to evaporate the solvent. The humidity of water is a factor between the surface tension of water and the body to be printed. Water naturally forms a minimum surface area that is adjacent to the boundaries of the body so that it cannot be wetted. The drying of the aqueous ink has two kinds of absorption of the printed body and no absorption of the printed body, and it is clear that the ink is not absorbed by the printed body such as the plastic film. Even if the absorbed body can absorb a considerable amount of water, if the water and the resin are not completely absorbed and separated when dried, that is, the water capacity of the printed body is saturated, the watermark ink that no longer absorbs the ink will not dry. At this time, if there is honing, there will be color transfer.
PH value is an extremely important factor in water-based inks. Lack of control or incorrect pH will cause many problems. PH is a method for measuring the acidity of solvents. The pH range is from 0-14, but it is not necessary. Too staring at the numbers 6, 7, or 8 or 9, because some people use 100, 800 or 900. What is the real attention? That is, the pH value affects the viscosity of the aqueous ink. In the typical aqueous ink, the general pH range should be between 8 and 9 as shown in the graph.
A few simple steps to control the ink:
Stir well before use.
Detect the ink viscosity of the printing press.
Adjust the viscosity and reconfirm the viscosity and pH.
Of course, there are other simple QCs that you can control to control the ink, even if there is a problem.