Discussion on Application Experience of Powder-free Ink Additives

I published "Printing Technology, Packaging, Decoration and Printing," published in November 2004. After publishing the "additional product of powder spraying process-composite offset printing ink additive", I was very gratified to receive widespread attention from readers in the industry. On the one hand, the product has achieved some results in the alternative powder spraying process in practical applications across the country, and achieved satisfactory results for the user in the overall printing process and overall (comprehensive) print quality and post-press process. . On the other hand, according to the feedback information, there are some problems in the accumulation of ink on the blanket. I personally summarize the problem and answer it as follows.

feedback

(1) When printing to 4000 sheets or so, the phenomenon of stacking began to appear, but no abnormal phenomena occurred in the ink transfer system and plate of the machine.
(2) More than 5,000 copies were printed, ink piled up, and other aspects were normal.
(3) When printing 9,000 sheets, everything was normal and there was no pile-up phenomenon.

In response to the above users' feedback, the printing companies in various regions have put forward their opinions on the number of printed matters (long-lived, short-lived), mainly including the following:

(1) Regularly printing 3,000 to 4,000 short-lived companies that are very satisfied with the product.
(2) The company that regularly prints long-lived products has two views on the product: First, it is satisfied that it can continue to print about 9,000 sheets; Second, although it is acceptable to continuously print about 5,000 sheets, it still wants to improve the continuous printing. the amount.
(3) Enterprises that pay more attention to equipment maintenance and maintenance are very satisfied because they have solved a maintenance problem for them.

(4) It is expected that on this basis, the product will be further improved.

Cause Analysis

Causes of heaping up of ink are mainly raw and auxiliary materials, environmental conditions and other factors. The phenomenon of pile-inking has certain rules. When problems occur, if we carefully observe the development trend, the progress of changes, the locations involved, and the degree of damage to the quality of printed matter, we can determine the following conclusions through phenomena.

1. Clockwise stacking ink

Stacking rollers, stack plates, and blankets, stacking ink from top to bottom, can be called the “three heaps” phenomenon. It is mainly caused by two single physical properties, one is that the ink itself is dried too fast or has added too much dry oil (especially red dry oil), which not only causes the ink crust, but also causes the ink texture to become thicker; The second is that the pigment particles in the ink are thicker and have a heavier texture.

2. Anti-clockwise stacking ink

The “three heaps” phenomenon begins with the pile-up phenomenon of the blanket, which is mainly caused by the interrelatedness of the properties of the two substances. The first is the surface strength of the paper, and the second is the viscosity and viscosity of the ink. Of course, if the viscosity of the ink on the printing press has a large added value, then it is another matter. In the course of this problem, the surface strength of the paper is determined by the surface strength of the paper compared with the larger viscosity and viscosity of the ink.

The ink pile caused by ink emulsification is first affected by the printing plate and the ink on the ink roller, and then it is developed in two directions, up to the ink fountain, down to the blanket and then transferred onto the paper. If the degree of ink emulsification is slight, it will not hinder, and if the ink is emulsified, it will cause a pile of blankets and an ink roller phenomenon. If the ink emulsification is too severe, the structure of the ink will be destroyed, resulting in the inability to print. However, what is easily overlooked is the progressive ink emulsification phenomenon, which is neither minor nor severe. At the beginning, there are no obvious signs of change. When the moisture content gradually becomes larger and accumulates to a certain degree, the ink will accumulate little by little on the blanket. At the same time, the ink roller is gradually transferred to the ink transfer system. The phenomenon is that the ink layer on the ink roller slowly thickens, but it does not reach the extent that affects the ink transfer and transfer. At this point, if you do not pay attention to adjust the balance of ink and water, miscalculate the root causes of the ink, and improper measures, it is prone to accidents.

With regard to the problem of non-powdered ink additives causing the ink to accumulate blankets, the feedback information and related data are to be comprehensively reviewed, and then verified to draw appropriate conclusions, and to implement product function improvements based on actual conditions.

Two suggestions

(1) Remove any residual dust that adheres to the components of the printing press. If you use powder-free ink additives, it should be completely removed.

(2) Regularly replace the dampening solution while thoroughly removing the sediment under the water tank and scrub the cabinet. The reverse development in the printing process is not only unique to the "three piles" phenomenon, but it is also found in dampening fluids, but it has not attracted people's attention. When encountering problems, the following methods can be used to detect the fountain solution: 1 After the fountain solution in the tank is left to stand for 4 hours, the fountain solution in the tank will be divided into upper, middle, and lower layers. 2 Mix the dampening solution in the water tank, and take out 150ml of glass that has been poured into 200ml. After standing for 4 hours, first pour out the upper and middle layers of water (be careful not to stir the sediment at the bottom). The lower part of the water was poured out, and the precipitate left on the bottom was taken out and placed on a glass slide. After drying to 80 percent, the microscope was used for observation. If you do not have a microscope, you can use a 30-fold magnifying glass to observe carefully and you can find the reason.

Ink problem <br> <br> winter temperature is low ink thickening of external factors. Under the influence of temperature, the thick change of the ink (primary ink) is a physical phenomenon, but the change is the morphology, not the essence (the basic performance of the ink).

The ink is too thick and the viscosity is large, but it is best not to use thinner or varnish to adjust its consistency. Because when the user needs to mix the ink, the total amount of various additives that the original ink produced by the ink manufacturer can accommodate is limited, beyond the limit amount, even if it can be used, it also weakens the basic performance of the ink, affecting the printing quality. In addition, the viscosity and the consistency of the ink are related. Here it refers to its properties and not to its phenomenon. In practice, this is often the case. The ink has a large consistency, but its viscosity is small, and its fluidity is still relatively large. Therefore, a large-consistency ink does not necessarily have a large viscosity, and a large-viscosity ink does not necessarily have a large consistency.

The thickening phenomenon of ink caused by temperature can be solved by the following methods: (1) The original ink is placed on the radiator or next to the heating, so that the temperature rises slowly and gradually returns to the original state. (2) External heating can be performed using boiling water in emergencies. The specific method is to pour boiling water into the basin, and then put the original barrel (box) ink in water, but to prevent water vapor from immersing, until the water temperature drops to around 27°C. Take it out, open the lid and stir it to use. The temperature of the printing shop is preferably kept at about 27°C.

The ink is also thick at normal temperatures because the consistency of the ink reflects the rheological properties of the ink to some extent. If it is not due to external factors caused by the phenomenon of thickening, can be summarized as the following two reasons: First, due to the strong thixotropy in the original structure of the ink caused by, but after stirring to restore the original state, can still be used; two expired ink or Deterioration inks due to improper storage cannot be used.

Source: "Printing Technology" 2005.2