1. What is the difference between the commonly used composite packaging printing inks?
At present, in the market, in order to meet the requirements of various composite materials, in addition to printing by a flexible printing machine, a method of copying a composite packaging material is mostly printed by a gravure printing machine. Due to differences in substrates (cellophane/plastic, paper/plastic, plastic/plastic, paper/metal foil, plastic/metal foil, cellophane/plastic/metal foil, etc.) and composites (dry paper/plastic, dry process) Paper/metal foil, etc., to distinguish the type of printing ink. For example, dry compound printing inks generally contain organic solvents with high volatility and are commonly used in chocolate, cigarettes, pharmaceuticals, and cooking and packaging foods.
Another example is wet printing inks. Since one layer of the composite material is a water-absorbing paper, the ink is mainly composed of sodium polyvinyl acrylate, chloroacetate copolymer resin, polyacrylate, natural rosin modified resin, etc. The alcohol type or water-based ink, which does not allow the printed ink film to be deformed due to water soaking in the water-based or water-based emulsion system, and cannot be affected by the mutual repulsion of the ink film and the adhesive. Degree, but also consider the adhesion of the ink and the substrate.
There are also extruded composite inks, which are mostly used for PP, PE and other packaging materials. The ink should take into consideration both the heat resistance of the adhesive and its adhesiveness to the adhesive, as well as the adhesion strength of the ink to the substrate. At present, there are polyamide-based inks that can be used as both surface and print presses, as well as lithographic polypropylenes with a strong acidity.
In addition, there are packaging printing inks that use hot-melt resin as a binder to meet the hot melt compounding method.
2. In ink production, what method can be used to determine the ink will not cause the migration of ink due to changes in the ambient temperature?
The author's approach to this issue, based on his own practice, is to first take the test (or production) ink and print it out with a color bar or a color wheel or ink proofer, and then wait for the ink film to dry and then print the sample ( The ink film is facing upwards) Placed on a metal whiteboard (coated with white ink, white paint, or white paint), then sealed with two layers of tape and compacted, open the electric furnace and place a pan or beaker on it, add water, until the water boils At the same time, put the sealed seal into boiled water, and immediately record the time. When it is boiled for one hour, take out the seal and uncover the tape and seal. Observe the patch on the bottom white metal plate. There is no color. If not, it means that the ink will not migrate the printed ink film in the past two years because of changes in the ambient temperature and humidity. Otherwise, the ink will not be reversed.
3. How to determine in a very short period of time that the printing ink is stable and has good leveling property (for example, the color becomes light after a certain period of printing or when the printer gradually increases the speed, the ink is from dark to light, and even the ink cannot be transferred. )?
A simple method is to drop 0.1 g of ink on top of a scraper (meter), and hold the blade (knife) at a 45° angle from top to bottom, and scratch it one at a time. This method is used three consecutive times. Observe whether the length of the ink scraped can have ink at the 0 micron scale value. If there is ink, the ink will not show the above-mentioned failure of the printing ink, otherwise it does not occur.
4. Is the light fastness of the printing ink not good, is it a pigment problem? What is the basis of the standard?
Printing inks have poor fastness to selenium, which is mainly a pigment problem, followed by the problem of the binder material of the ink system.
The standard is based on blue and gray cards, and is commonly used as a criterion for evaluating the light fastness and weather fastness of packaging printing inks. This method was used to evaluate the light fastness and weather resistance of textiles as early as the 1950s. Degree - that is, there are 8 kinds of light fastness, from level 1 to level 8 (see Chinese Chromatography), that is, the light fastness of level 1 is the worst, and the level 8 is the highest. And when testing, put the sample and standard sample together and observe the level of change.
5. Does ink drawing affect print quality?
In general, although the drawing (ie, generally speaking, viscoelastic) ink has a good stability, it often causes the flying ink to be ejected under the action of centrifugal force after high-speed printing. Dirty prints. So a good ink, whether gravure, emboss or offset ink, requires no drawing or pulling. In order to prevent the ink from stretching due to its own cohesive force and extend the filament, and finally break in the middle. Therefore, it is also used as an indicator to evaluate the quality of ink.
6. How does the attraction between the ink and the substrate result?
It is mainly produced by the interatomic forces (chemical bonds) and intermolecular forces (hydrogen bonding forces and van der Waals forces) in the ink system, as well as the forces generated by the printing machinery and the electrostatic attraction at the substrate interface. The attraction between things is generated.
7. What are the characteristics and classification of packaging printing ink colors?
According to the author's knowledge, the color characteristics of packaging printing inks are hue, brightness (brightness), saturation (saturation). The classification of packaging printing ink color is: color and non-color two major categories (color refers to the color other than black ink, white ink and gray ink; non-color refers to black ink, white ink and gray ink with intermediate colors) .
8. When can I determine the proper amount of ink defoamer?
In general, before the batch production of ink, a small sample test should be conducted first. After the tested inks are tested and recorded on the technical indicators, they are to be tested after the next day (ie 24 hours). The method was measured once. The last time is the actual technical specification of the ink.
However, in our actual production, some small ink companies do not have dedicated laboratories or test tools. The author's experience is that during the same test method mentioned above, two items need to be added (one is to put the produced ink on With hot or cold water, when the temperature of the ink reaches 25°C, the above items are detected, and finally, two consecutive times are performed to obtain the average value, that is, the actual data of the ink. Only in this way can the balance between defoamer performance and shrinkage cavities be achieved. Otherwise, the defoamer will be mistakenly thought to be added in excess, often resulting in oxygen bubbles being more difficult to eliminate and causing shrinkage in the printing.
Reprinted from: China Packaging News