The production and solution of ink skins

Ink skin phenomenon is a kind of oxidation conjunctivation phenomenon of connecting materials in ink. The conjunctivation is the same as that of ink drying, and is also affected by factors such as temperature, humidity, oxygen in the air, and the content of desiccant in the ink. Simply speaking, the condensation phenomenon of ink is actually a kind of oxide conjunctivation phenomenon of ink that we don't want to see (because it occurs when we don't want conjunctivation)
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there are many factors that can lead to ink skining, but it boils down to several categories: high levels of dry oil in ink, temperature, and prolonged contact between ink and air. Let's do some analysis separately.
, the ink in the dry oil content is too high
generally in the process of manufacturing ink or printing process may have such a mistake. Add a desiccant Be sure to add it in moderation in combination with printing conditions and ambient temperature, otherwise the ink will dry out when you don't want to dry (skin). As for the use of desiccants, it is no longer repeated here.
, due to temperature causes
by the temperature of the ink skin, mainly caused by high temperature. Unsaturated molecule activity in the ink increases when the temperature is too high, especially the part of the surface that comes into contact with the air is more likely to be oxidized by the conjunctivation under the effect of oxygen. There are several aspects to the high temperature said here:
A. Ambient temperature is too high, according to our experience, the general summer ink skin phenomenon is much more obvious than in winter, if there is no air conditioning in the workshop is more obvious. Reasonable control of the temperature of the working environment is necessary, in general, the temperature of the workshop can be controlled at about 20 degrees C is more ideal temperature, that is, to ensure the good flow and transfer performance of the ink, but also to control the ink skin at a relatively low degree.
B. When the temperature on the machine (e.g. between the ink rollers) is too high, the ink will also appear in the printing process skin phenomenon. When the contact pressure between the ink rollers is too large, the temperature increase is more obvious, this time the ink is easy to appear on the ink bucket and ink roller skin phenomenon.
and control the pressure between ink rollers is very important to prevent ink from peeling during printing.
C. The air leaking from the dryer drys the surface of the ink, or the hot wind blows into the ink in the ink bucket.
D. is also caused by other abnormal heating of the machine.
3. Due to the long time of ink and air contact caused by
several conditions of skin production
the connection material in the ink can react with oxygen in the air redox reaction, exposure to the air for too long will of course be oxidized, the phenomenon of skin. Generally this skin mainly has the following:
A. temporarily unused ink, exposed in the air, a long surface will appear thick oxide film. We will have this experience in the printing plant, when from cartridges or cartridges outward ink, to try to keep the surface of the ink in a flat state, the reason for this is to minimize the contact area of ink and air, so that even after the ink conjunctivation waste will be as small as possible. Then the remaining ink with a protective film re-covered, blocking contact with the air, which can also effectively prevent the ink skin phenomenon.
B. printing press for a long time, there is no cleaning ink road, resulting in ink in the ink roller and ink bucket skin. In the work must pay attention to when a long time downtime, to clean the ink road, when the downtime is not very long, you can choose to spray ink anti-cortide on the ink road.
C. ink in the ink bucket if not stirred for a long time, there will be skin phenomenon. In the printing process we often say that "three diligence" in which the ink in the ink fight is very important, first of all, it can maintain the ink in the ink bucket very good flow, and secondly, it can make the surface ink and internal ink exchange frequently, to avoid contact with the air ink is always the same part. Standardized operation for ink volume adjustment, the basic criteria for ink adjustment are: the gap between the ink bucket blade and the ink bucket roller as small as possible, the corner of the ink bucket roller as large as possible. This is also partly based on the above considerations.
D. ink roller structure is not good, resulting in non-flowing stranded parts. As b says, this also causes a certain part of the ink to remain in contact with the air, so that the skin is inevitable.
The effect of ink skins on printing
the skins formed during normal ink storage and those that appear during the printing process often cause a lot of annoyance to printers and printer operators, such as higher printing costs and lower printing product quality. It is of great significance for printing enterprises to be able to control the skining phenomenon of ink effectively in the pre-press and printing process.
when the ink skin phenomenon is serious, first of all, will have a great impact on the stability of printing costs. It is calculated that the light waste 1 per cent and the heavy 1 per cent. This tangible consumption adds a heavy economic burden to the packaging and printing enterprises. Secondly, the impact on the quality of printed products can not be ignored. When the printing process ink skin, ink skin will be under the role of rolling pressure to the transmission of ink distribution of all links, the impact on the normal ink transfer is very large, at the same time when the ink skin adheres to the plate ink roller, will make the plate on the map of the density of the mutation; When the ink skin is transferred to the plate and rubber cloth, it will cause ring marks on the print, when the ink skin adheres to the water roller, it will make the water transfer abnormal, the appearance of dirty phenomenon, the ink skin may also be attached directly to the surface of the paper.
to solve the problem of ink
so how to effectively deal with the failure of ink skin in printing? The following are some of the more common methods used in printing operations.
(1) cannot be used to dry too fast ink;
(2) to add slow-drying solvents and other supplements;
(3) to replace the damaged ink;
(4) in the ink bucket non-stop stirring;
(5) on the ink bucket to set a closed top cover;
(6) adjust the hot blow angle. People with a little printing common sense know that when the drying too fast, ink concentration is too light, poor flow, ink denaturation or ink static electricity, the printing press speed is fast, that is, to prevent ink in advance on the plate drying, but also overcome the packaging printing ink into ink formed skin, but also eliminate the pattern failure of the text.
ink nodding agent
In the work of preventing ink skining, adding ink anti-corting agent to the ink is an important means. Facing the use of ink anti-cortical agent in printing and note to do some introduction:
printing ink oxidation, modified resin oil, the use of pigments, fillers, drying agent dosage, ink finished product storage when the ambient temperature, humidity and other factors have a certain degree of ink skin Therefore, in the use of anti-cortical agents, we must take into account the above factors, but also pay attention to the addition of the following seven aspects of the basic knowledge:
addition
generally calculated by ink (because the main component of the skin is the main raw material of ink) or according to the total amount of printed ink, but also to take into account the impact of other components.
usually add between 0.1 and 0.3%. Because of the difference in temperature and humidity all year round, there is a difference in the speed of its skin. Therefore, 0.1% in winter, 0.3% in summer and 0.2% in spring and autumn, depending on the ingredients of the formula is scientific.
Ink film drying rate
We have proved in practice: in the offset ink made of alicyl acid resin, the amount of methyl ethyl is generally 1%, although the drying speed is slightly longer, but still within the standard range of printing regulations. This is due to the additive formed by the aid and the drying agent, so that the reason for the temporary loss of activity of the detergent, so different from the traditional use of phenolic compounds to capture the activity of free termination polymerization reaction principle. Therefore, the effect of such compounds on the drying rate is not very large, if the dosing is too much, the volatility time is prolonged, the complex disintegration is too slow, often affect the packaging printing ink filming speed.
yellowing
anti-cortical agent once more than 0.3%, often lead to printing ink film yellowing. Especially when used in white ink, after a long period of storage will produce a yellowing phenomenon, so strict control of the amount added or changed to butaldehyde can avoid the occurrence of yellowing phenomenon.
Chromicity
ink in addition to anti-cortide, often directly affect the color of ink, usually ink oil impact is greater than color ink, white or yellow ink impact is greater than dark color ink. Generally this phenomenon is difficult to observe by visual inspection and is independent of the amount added. Although we already know that the drying of printed graphics has no effect on the application of ink film hues, but in the presence of certain pigments (such as sex pigments) and drying agents, packaging printing of color graphic ink film tones will appear significant differences, the tone of the problem. When we encounter this situation, we should continue to sample ink, first do color difference test, the purpose is to avoid color change after printing affect the appearance of the ink film quality.
Printed ink film state
Although the anti-cortical agent will not have any effect on the state of the printed ink film, but in the long-term storage of ink, will be delineation, resulting in turbidity after the ink film and affect the gloss of the ink. If the above material and ink system in the connection material, pigments, fillers and drying agent design ratio is not right, there will be larger particles. In this regard, should be tested before printing.
use method
anti-cortide is generally added when inking, and at room temperature and stirring side to add. For volatile inks, in order to control ink, color materials in the grinding dispersion and storage period, especially during the printing process skin, can be used in ink printing to add a part, before printing to add a part is appropriate.