Most popular master ink technical knowledge, grasp

2022-09-21
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Master the technical knowledge of ink and grasp the quality of packaging and printing

1 How to distinguish the printing ink of composite packaging

at present, in the market, in order to meet the requirements of various composite materials, the replication methods of composite packaging materials are mostly printed by gravure printing machines except flexible printing machines. Due to the difference of substrates (cellophane/plastic, paper/plastic, plastic/plastic, paper/metal foil, plastic/metal foil, cellophane/plastic/metal foil, etc.) and composite materials (dry paper/plastic, dry paper/metal foil, etc.), the types of printing inks are distinguished. For example, dry composite printing inks usually contain volatile organic solvents, which are usually used in chocolate, cigarettes, drugs and cooking food packaging and printing materials

another example is wet printing ink. Because one layer of the composite material is absorbent paper, this kind of ink is mainly alcohol or water-based ink with polyvinyl alcohol sodium silicate, chloroacetic copolymer resin, polyacrylate, natural rosin modified resin, etc. as the binder. This kind of ink cannot cause deformation by wetting the ink film after printing with the water of the composite water-based or water emulsion composite adhesive system, We should not affect the composite fastness due to the mutual exclusion between the ink film and the composite adhesive, but also consider the adhesion between the ink and the substrate

there are also extrusion composite inks, which are mostly aimed at PP, PE and other packaging materials. This kind of ink should consider not only the heat resistance and adhesion of the adhesive, but also the adhesion strength of the ink on the substrate. At present, there are polyamide based inks that can be used for surface printing and extrusion, as well as chlorinated polypropylene based inner printing inks with strong acidity

in addition, there are packaging printing inks with hot-melt resin as binder to adapt to the hot-melt composite method, etc

2. In ink production, what method can be used to judge that ink will not migrate due to changes in ambient temperature

in view of this problem, the author introduces the method based on his own practice: first take the tested (or produced) ink and print out the print sample with a color developing rod or wheel or an ink proofing machine, then wait for the ink film to dry, put the print sample (the ink film faces up) on the metal whiteboard (coated with white ink, white paint or white paint), then seal two layers with tape and compact it, turn on the electric stove and put a pot or beaker on it, add water, and wait for the water to boil, Then put the sealed printing sample into boiling water and record the time immediately. Take out the printing sample after boiling for an hour, uncover the adhesive tape and printing sample, and observe whether there is color on the white metal plate at the bottom. If not, it means that the ink will not migrate the printed ink film due to changes in ambient temperature and humidity within two years, otherwise, it is the opposite

3. How to judge in a very short time that the printing ink is stable and has good leveling (for example, the color becomes lighter after printing for a period of time or when the printing machine gradually accelerates, the ink changes from thick to light, or even cannot transfer the ink)

a simple method is: drop 0.1g of ink on the scraper fineness meter (meter), and repeat it by hand. Hold the scraper (knife) at an angle of 45 ° from top to bottom and scrape it in one breath. This method is used for three consecutive times, and then observe whether the scraped length of the ink can have ink at the scale value of 0 μ M. if there is ink, the ink will not have the printing ink failure mentioned above, otherwise, it is the opposite

4. Is the poor light fastness of printing ink a pigment problem? What is the basis of the standard

the poor selenium fastness of printing ink is mainly due to the pigment problem, followed by the binder problem of the ink system

the standard is based on the blue card and gray card, which are commonly used as the standard for evaluating the light fastness and climate fastness of packaging and printing inks. This method was used as early as the 1950s to evaluate the light fastness and climate fastness of Textiles - that is, there are eight kinds of light fastness, from grade 1 to grade 8 (see the national chromatogram on heat dissipation for details), that is, grade 1 has the worst light fastness and grade 8 is the highest. During the test, put the printed sample and the standard sample together and observe their change level

5. Will ink drawing affect the printing quality

generally speaking, although the ink of wire drawing (commonly referred to as viscoelasticity) is more stable, it is often easy to cause ink flying and splashing dirty prints under the action of centrifugal force after the filament pulled out by the ink breaks during high-speed printing. Therefore, a good ink, whether gravure, embossing or offset printing ink, requires no wire drawing or wire shortening. To prevent the ink from stretching into silk due to its own cohesion after being stretched, and finally breaking in the middle. Therefore, it is now also used as an indicator to evaluate the quality of ink

6. How does the attraction between ink and substrate come into being

is mainly caused by the force between atoms (chemical bond) and molecules (hydrogen bond force and van der Waals force) in the ink system, as well as the force of printing machinery and the attraction between the ink and the substrate generated by the electrostatic attraction of the substrate interface

7. What are the characteristics and classification of the color of packaging printing ink

as far as I know, the color characteristics of packaging printing ink are hue, lightness (brightness), saturation (chromaticity). The colors of packaging printing inks are classified into two categories: color and non color (color refers to the colors except black ink, white ink and gray ink; while non color refers to black ink, white ink and gray ink with intermediate color)

8. When can we determine the appropriate amount of ink defoamer

generally speaking, before batch production of ink, small sample test should be carried out first. After the ink tested is tested and recorded, the same test method mentioned above should be carried out again the next day (i.e. 24 hours). Generally, the last time Li Jianbo points out is the actual technical index of the ink

but in our actual production, what if some small ink enterprises do not have special laboratories or test tools? The author's experience is that in the process of the same test method above, two items need to be added (one is to put the produced ink in hot or cold water, and then test the above items when the ink temperature reaches 25 ℃, and finally carry out it twice in a row to calculate the average value, that is, the actual data of the ink). Only in this way can the balance between the performance of defoamer and shrinkage be achieved. Otherwise, it will be mistakenly thought that defoamer is insufficient and will be added too much, which will often make it more difficult to eliminate oxygen bubbles and cause the printing failure of shrinkage

reprinted from: China Packaging News

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