New environmentally friendly fountain solution

Offset printing is a process of ink and water balance and a complex chemical process. There are many factors that affect this process. One of the important factors is water, the fountain solution. The quality of the fountain solution directly affects the quality of the printed matter.

The main components of the fountain solution are inorganic acid salts, wetting agents, plate protectants, preservatives, defoamers, and the like. The inorganic acid salt is a buffering agent in the fountain solution system, which plays a role in stabilizing the pH value. Because the pH value changes, the printing ink resistance, the ink balance, and the drying speed of the print in the offset printing plate have an influence. Most fountain solutions use phosphates, nitrates, dichromates, etc. as buffers. Its characteristics are low cost, easy preparation, can meet the basic requirements of offset printing, suitable for low-grade prints. However, the disadvantages are also obvious. If the surface tension is higher than normal water, the wetting effect on the layout is not good: the corrosion is strong and the buffering effect is poor; the ink balance is not easy to control. At present, this fountain solution has tended to be eliminated.

There is now a new type of fountain solution using organic citric acid as the main raw material. This organic weak acid type fountain solution not only satisfies printing requirements, but also greatly reduces the corrosion of printing plates and printing machine metal parts, and solves the problem of printing. In the course of the process, water and ink are large and the balance between water and ink is not easy to control. The main role of this new fountain solution in the offset printing process is as follows:

1. Maintaining ink and water balance

Only when there is a clear demarcation line between the water film of the non-graphic part of the plate and the ink film of the graphic part, the balance of offset ink can be achieved. In actual production, the ideal ink-water balance does not exist. In general, the less the amount of fountain solution used in the printing process is, the better the printing process is. Therefore, the wetting agent in the fountain solution plays an important role. The wetting agent used in this new dampening solution can very well reduce the surface tension of the fountain solution. The water is evenly distributed in the non-graphic part of the printing plate to achieve a good wetting effect. The new fountain solution not only greatly reduces the amount of water and alcohol used, but also reduces the pollution to the working environment, saving the company's production costs.

2. Clean layout

The dirt on the plate during offset printing mainly comes from the substrate. Most papers are weakly alkaline. Each time the paper is printed, water and ink on the blankets are carried on. At the same time, some weak alkaline stains are left on the blanket. These dirts are directly transmitted by the blanket. On the printing plate, if it is not promptly removed, it will erode the graphic part of the printing plate, causing the diazonium compound layer of the oleophilic layer to fall off, resulting in the loss of dots; at the same time, the non-graphic part of the hydrophilic organic salt layer will be worn out, resulting in layout. Dirty and other printing problems. The new organic weak acid fountain solution solves these problems well. First of all, the organic acids in the fountain solution can neutralize the weakly alkaline dirt, protect the printing plate graphic part to the greatest extent, and maintain the lipophilicity; second, brush off the paper, paper dust, etc. on the printing plate. The object reduces the wear of the non-graphical part of the printing plate by the dirt, maintains its good hydrophilicity, ensures the continuous printability of the printing plate, guarantees the quality of the printed product, and improves the printing plate's resistance to printing forces.

3. Reduce the layout temperature

In the high-speed operation of the offset printing press, the printing plate continuously rubs against the ink roller and the blanket to generate a large amount of heat. This heat will reduce the viscosity of the ink, change the rheology of the ink, and cause printing failures such as flying ink, drying, and plate printing. . The fountain solution absorbs these heat and volatilizes the water and alcohol in the fountain solution to dissipate the heat, effectively control the layout temperature, and keep the ink temperature stable, achieving the purpose of ink and water balance.

In summary, to control the balance of ink and water, the amount of fountain solution added is an important factor that cannot be ignored. Strictly control and manage the amount of fountain solution. In addition to the method of controlling the pH of the fountain solution and the amount of alcohol added, the conductivity of the fountain solution can also be used to control the concentration of the fountain solution. When the concentration of the fountain solution increases, the conductivity value increases linearly in a certain proportion, but the pH decreases as a curve. Within a certain range, although the concentration of the fountain solution increased, the pH value did not change. This shows that conductivity is more accurate than the pH value to express changes in fountain solution concentration. Only by properly controlling and controlling the pH value of the fountain solution, the amount of alcohol added, and the concentration of the fountain solution can the production cost be reduced, thereby creating a greater profit margin for the company.

Reprinted from: China Ink Online