Dairy plastic packaging printing fade problem

A good packaging must have good printing cooperation in order to play a good role in packaging, in order to arouse people's desire to buy. However, products with ambiguous printing and missing (fading) characters and patterns will not be recognized by consumers.
Ultra-high strength liquid film is made of high-pressure polyethylene (LDPE) and linear polyethylene (LLDPE) with a certain proportion of milk white masterbatch. It is made by blown film equipment. The milk film products on the market are milky white film, Black and white film, pearl film, high barrier film, etc., printing inks generally use polyamide inks, it is more compatible with polyethylene in many types of ink, to make printing does not fade it must be on the liquid film The production process is strictly controlled and tested.
I. Precautions for film production 1. The raw materials used for film blowing must be new materials. Recycled recycled materials must not be used.
The solution of the recycled material has been destroyed, and when the film is mixed with a new material, the heat-sealing property of the film will be reduced, sand holes will be generated, the number of broken packages will increase, and the smoothness of the film surface will decrease. In order to improve the smoothness of the film surface, some manufacturers add an excess amount of oleic amide type slip agent to the blown film raw material, which will cause the surface tension of the film to decrease, and the binding fastness of the ink is naturally difficult to guarantee.
2. Blown film temperature The optimum extrusion temperature of blown film is from 160°C to 180°C. Excessive temperature will cause the material content to seep out and affect the surface tension of the film. If the temperature is too low, the film processing will be unstable. Reduced production.
3. The corona treatment on the film surface The principle of corona treatment is that the film passes between two electrodes with high pressure. The high pressure causes the air between the electrodes to ionize, causing electron flow between the electrodes. The electrons are marked on the surface of the film and cannot be seen by the naked eye. The pits make the surface of the film polar so as to facilitate printing ink adsorption.
The surface polarity (ie, surface tension) of the film can be tested with dyne. Generally, the surface tension of the film just after corona treatment should reach 40 dynes or more. After the film is placed for one week, it must reach 38 dynes or more, lower than 36. Dyne's film has no sorption fastness to the ink.
4. Storage of film In general, the film is best used within one week after the completion of the blowing. It must be stored for a long time. It must also be stored in a dry, cool and ventilated warehouse. The maximum length cannot exceed 3 months. Before the film is used, it must pass the dyne test and it can be used only after it is qualified, otherwise it will cause losses.
Second, some of the printing process precautions Bad printing process is the key to ink fade, generally after the use of suitable table printing ink and appropriate solvents, printing still need to pay attention to the following points:
1. The proportion of ink must be changed according to changes in the environment.
Inappropriate solvent ratios can cause ink drying difficulties and surface “sham dry”. False dryness means that the solvent with high volatility in the solvent ratio of the ink has volatilized, the volatile substance is not completely volatilized, the surface of the ink is dry and the ink is left for a period of time after printing, the residual solvent continues to infiltrate, and ink adhesion and discoloration occur. .
2, printing speed and drying oven temperature.
The printing speed should not be too fast. Generally, it is better to control the temperature at 30 meters per minute. The drying oven temperature is generally 30 to 40 DEG C. This is to allow the ink solvent to cure and volatilize, and to enhance the ink adhesion fastness.
3. The environment of the printing shop The environment of the printing shop must ensure a certain humidity (between 60% and 70% is preferred), good ventilation is required, and the temperature is preferably 25 to 30°C. An excessively dry environment can cause static electricity in the film. Difficult to release, too humid environment will make it difficult to volatilize ink and decrease its fastness.
Third, after the process of printing the finished product is best placed after a day and then cut, this is conducive to the full cure of the ink, and improve the ink fastness.
After the above processes in the production have been strictly controlled after the detection, the fastness of the ink can generally meet the requirements, but due to the printing of the film, the ink on the surface of the film is vulnerable to various damage, water, acid , machinery, friction more or less will cause the ink to fade, Moreover, after the filling of the milk is completed, generally need to be placed in a refrigerator at 4 °C refrigerated, after taking out the refrigerator from the refrigerator, the surface of the film due to hot and cold, Condensation can occur. During transportation, bags and bags are rubbed by vibrations. They are in the hands of consumers, and some need to be heated to drink milk. Such a process requires the ink to be very resistant to freezing and water at the same time. Sex, heat resistance and abrasion resistance, and such ink products are very difficult to produce, so far, no ink can fully meet the above four characteristics.
To completely solve this phenomenon, only the surface printing into India, the ink is not on the surface there is no need to worry about color, there are three ways: The first is the composite milk film structure outside the BOPP / printing / PE, such a structure required There are special filling equipment, the cost is also higher, each bag costs to reach 0.10 yuan / only about), the second film structure is PE / printing / PE, such a structure of ordinary filling equipment can also be filled , But the cost is still relatively high, each bag must be 0.08 yuan / only, the third method is cast PE / printing / PE structural film, that is, after the original milk film printing is completed, add an additional process, flow in the printing surface A thin layer of transparent thin film, this is a product structure specially developed by our company based on the actual use of customers. Its advantages are:
1. The ink layer is protected by laminating and there is no fear of discoloration, and the brightness of the ink is very good due to the high transparency of the lamination film;
2. Due to the film's isolation from the contamination of the milk with toxic substances such as ink and residual solvents, the odor is eliminated and the sanitation is greatly enhanced;
3, due to the film, some of the original film on the trachoma is also covered, the leakage rate is almost zero. Its only drawback is that its cost is increased by 1,500 yuan per ton compared to ordinary films, but it only adds 0.005 yuan to the cost per bag. Compared with the films of the first two structures, its advantages are more obvious.
If the milk manufacturer is more concerned about the problem of ink discoloration, the use of composite film packaging is still more feasible.