The answer to the application of powder-free offset printing ink additive
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With the replacement of the powder-spraying process, the composite offset printing ink additive has achieved some success in the alternative powder spraying process in the practical application throughout the country, and in the whole process of printing process and overall (comprehensive) printing quality and post-press process On, it has achieved the effect of making users more satisfied. On the other hand, according to the feedback information, there are sometimes some problems in the ink accumulation blanket, and the problem is now summarized and answered as follows.
Feedback
(1) When printing to about 4000 sheets, the phenomenon of ink accumulation began to appear, but there was no abnormality in the ink transfer system and printing plates of the machine.
(2) Printing to more than 5,000 sheets, stacking ink occurs, and other aspects are normal.
(3) When printing 9000 sheets, everything is normal and there is no ink accumulation.
Cause Analysis
The main reasons for the accumulation of ink are: raw and auxiliary materials, environmental conditions and other factors. There are certain rules in the phenomenon of ink accumulation. When problems occur, if the development trend, the progress of the change, the location involved, and the quality of the printed matter are seriously observed, the following conclusions can be determined through the phenomenon.
1. Clockwise ink stacking
Stacking rollers, stacking plates, pile blankets, stacking ink from top to bottom can be called the “three piles” phenomenon. It is mainly caused by two single physical properties. First, the ink itself is dried too fast or excessive dry oil (especially red dry oil) is added, which not only causes the ink to crust, but also causes the ink texture to become thicker; Second, the pigment particles in the ink are thicker and heavier in texture.
2. Counter-clockwise stacking
The "three piles" phenomenon begins with the accumulation of ink on the blanket, mainly caused by the correlation of the properties of the two substances, one is the surface strength of the paper, and the other is the viscosity and viscosity of the ink. Of course, if the viscosity of the ink on the printing press is large, then it is another matter. In the process of this problem, the surface strength of the paper is in contrast to the greater viscosity and viscosity of the ink, and the decisive factor is the surface strength of the paper.
The ink piled up by the emulsification of the ink is first affected by the ink on the printing plate and the inking roller, and then developed in two directions, up to the ink fountain, down to the blanket and then transferred to the paper. The degree of emulsification of the ink is slight, and the heavy one will produce a pile of blanket and a stack of ink rollers. If the ink is too emulsified, the structure of the ink will be destroyed, resulting in failure to print. However, what is easily overlooked is the progressive ink emulsification which is neither mild nor serious. There is no obvious sign of change at the beginning. When the moisture content gradually increases and accumulates to a certain extent, the ink will accumulate on the blanket little by little. At the same time, the ink is gradually transferred to the ink transfer system. The phenomenon is that the ink layer on the ink roller is slowly thickened, but it does not reach the extent of affecting ink transfer and transfer. At this time, if you do not pay attention to adjusting the balance of ink and water, misjudging the root cause of it, if the measures are not correct, it is prone to accidents.
Regarding the problem that the ink-free ink additive causes the ink to accumulate the blanket, the feedback information and related materials are relatively comprehensive, and then the argument is reached to draw an appropriate conclusion, and the product function improvement is implemented according to the actual situation.
Two suggestions
(1) Remove residual dust adhering to various parts of the press. If you use a powder-free ink additive, it should be completely removed.
(2) Regularly change the dampening solution, and at the same time completely remove the sediment under the water tank and wash the box. The reverse development in the printing process is not only unique in the "three piles" phenomenon, but also in the dampening solution, but it has not attracted people's attention. When encountering problems, the dampening solution can be detected by the following methods: 1 After the dampening solution in the water tank is allowed to stand for 4 hours, the dampening solution in the water tank is divided into upper, middle and lower layers. 2 Stir the dampening solution in the water tank, take out 150ml and pour it into a glass cup with a capacity of 200ml. After standing for 4 hours, pour the water from the upper and middle layers first (be careful not to stir the sediment at the bottom), slowly Pour out the lower water, take out the sediment left at the bottom and spread it on the glass piece. After drying it, dry it and observe it with a microscope. If you don't have a microscope, you can use a 30x magnifying glass to observe it carefully.
Ink problem
Low winter temperatures are an external factor in which the ink thickens. Under the influence of temperature, the thick change of the ink (original ink) is a physical phenomenon, but the change is the form, not the essence (the basic performance of the ink).
The ink is too thick and has a high viscosity, but it is best not to use thinner or varnish to adjust its consistency. Because when the user needs to adjust the ink, the total amount of various additives that the ink manufacturer can produce is limited, beyond the limit, even if it can be used, it also weakens the basic performance of the ink and affects printing. quality. In addition, the viscosity and consistency of the ink are related, here is the nature rather than the phenomenon. In practice, this is often the case, the ink is thick, but the viscosity is small, and its fluidity is still large. Therefore, an ink having a large consistency does not necessarily have a large viscosity, and an ink having a large viscosity is not necessarily thick.
The phenomenon of ink thickening caused by temperature can be solved by the following methods: (1) Place the original ink on the radiator or next to the heating, and slowly warm it up to gradually return to its original state. (2) When using in an emergency, you can use boiling water for external heating. The specific method is to pour boiling water into the basin, and then put the original barrel (box) ink in the water, but prevent the water vapor from immersing, when the water temperature drops to about 27 degrees Celsius. Take out, open the lid and mix well to use. The temperature in the printing shop is preferably maintained at around 27 degrees Celsius.
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, it can be summarized into the following two reasons: one is caused by strong thixotropic in the original structure of the original ink, but can still be used after being restored to the original state by stirring; Deteriorated inks due to improper storage cannot be used.