Talking about the basic knowledge of water-based ink system
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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 body and then dry.
Of course, the solvent of the aqueous ink 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. More than a hundred pigments are formulated in inks to cover the spectrum of all colors, but in normal use, typical ink formulations are limited to about 50.
Several color pigment manufacturers 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 alkaline water.
The third element of the 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 printed body, when the resin and the 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 added stagnation, and the pH, hardness, and softness of the water all affect the drying property. 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 material 10%
·Additive 5%
·Resin 15%
Of course, this is only a rough value, and the final decision must be made according to the requirements of ink and printing quality. Nowadays, for high-quality flexible 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 idea of ink is already there, but I have to declare that this is the simplest version. Let's go back to the viscosity problem, and 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.
Viscosity is easily measured in the measuring cup, but care must be taken in temperature changes and the cleaning and protection of the measuring cup.
In terms of drying, evaporation of water is a very 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 absorbs both the printed body and the non-absorbed ink, and it is clear that the water is not absorbed by the printed body such as the plastic film. Even if the absorbed ink 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.
The pH value is an extremely important factor in water-based inks. Lack of control or incorrect pH will cause many problems. The pH is a measure of the acidity and alkalinity of the solvent. The pH range is from 0 to 14, but it is not necessary to stare at the number 6, 7, or 8 or 9, because 100, 800 or 900 are also used. What is the real attention? That is, the pH value affects the viscosity of the aqueous ink. In the typical aqueous ink, it can be seen from the graph that the general pH range should be between 8 and 9.
A few simple steps to control the ink:
• Stir well before use.
• Detect the ink viscosity of the upper press.
• Adjust the viscosity and reconfirm the viscosity and pH.