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.
First, the film production precautions
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 control
Blown film raw material extrusion temperature of 160 ~ 180 °C, high temperatures will cause the raw material content to seepage, affect the surface tension of the film; temperature is too low will make the film processing instability, yield decreased.
3, film surface corona treatment
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 become small pits that cannot be seen by the naked eye, so that the film surface is formed. Polarity for easy 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, the film storage
In general, the film is best used within one week after the completion of the blowing process. 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 long-term stacking, the film must be used. After the dyne liquid test, it can be used only after passing the test, otherwise it will cause losses.
Second, some of the printing process precautions
Poor printing process is the key to ink discoloration. Generally, following the use of suitable table printing inks and appropriate solvents, the following points must be noted when printing:
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 dryâ€. 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 printing shop environment
The printing shop environment must ensure a certain degree of humidity (between 60% and 70% is preferred), requires good ventilation, and the temperature is preferably 25 to 30°C. An excessively dry environment can cause the static electricity of the film to be difficult to release, and it is too humid. The environment makes it difficult to volatilize the ink and the fastness decreases.
Third, the latter process
It is better to place the printed product after it is placed for one day, which is beneficial to the full curing of the ink and the improvement of the fastness of the ink.
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 (see Figure 1), the second membrane structure is PE / printing / PE, this structure of ordinary filling equipment Can also be filled, but the cost is still relatively high, each bag must be 0.08 yuan / only (see Figure 2), the third method is cast PE / printing / PE structural film (see Figure 3), that is, in the original milk After the printing of the film is completed, an additional process is added to flow a thin layer of transparent thin film on the printing surface. This is a product structure specially developed by our company based on the actual use of customers. Its advantages are: 1, the ink layer laminating protection, no discoloration of worry, but also due to the high transparency of the film, so the ink brightness is very good; 2, due to the film to isolate the ink and residual solvents and other toxic substances Contamination of milk eliminates odors and enhances sanitation. 3. Due to the coating, some sand holes on the original film are also covered, and 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.
Fiber Insulation Tape,PVC Electrical Tape Co., Ltd. , http://www.hb-pvctape.com