Printed milk packaging films generally use polyamide type table printing inks. Such inks have good affinity with polyethylene films, good ink gloss, high attachment fastness, heat resistance, grease resistance, water resistance, etc. it is good. Milk packaging film is usually printed by means of surface printing, in addition to the general technical requirements of surface printing ink (such as hue, fineness, viscosity, drying, etc.), due to the ultra-high temperature instant sterilization in the automatic filling process ( ULTRA Temperature Sterilization (UHT) and H2O2 sterilization, therefore, this special bactericidal condition puts forward special requirements for the performance of the ink. What needs special emphasis here is the performance of the following aspects:
1. Strong adhesion to polyethylene film. Due to the smooth surface of the plastic film, the ink cannot penetrate the surface, so the adhesive force between the ink and the plastic film is required to be very strong, that is, the ink used for the printed milk packaging film should have the same effect on the substrate materialâ€”the polyethylene film. High affinity and tackiness, strong adhesion, and good print fastness are prerequisites for high quality prints and good printing results.
2. Strong abrasion resistance and scratch resistance. Because the printing ink is printed on the outer surface of the film, it will be subject to friction during the circulation of the goods. This requires that the printing ink used must have strong abrasion resistance and scratch resistance, and the surface strength of the ink film after printing. High, firm, and resistant to friction, otherwise the ink layer will fall off, resulting in incomplete print patterns, affecting product appearance and quality.
3. Has excellent water resistance. When the milk packaging film is subjected to ultra-high temperature instantaneous sterilization (140Â°C/1 to 3 seconds) and hydrogen peroxide sterilization, its surface will be exposed to water or water vapor. Therefore, it is required that the printing ink used must have excellent water resistance. Discoloration occurs.
4. Excellent heat resistance and freezing resistance. The printing ink used in the milk packaging film must have a certain degree of heat resistance, so as to ensure that the ink does not soften, stick, fade, discolor, etc. after the ultra-high temperature sterilization treatment. In addition, the milk after filling is generally required to be cold-stored in the preservation, circulation, and sales. Therefore, it is required that the printing ink used must have good freeze-resistance performance, and the freezing and shedding of the ink layer should not occur at a low temperature. .
5. Outstanding antioxidant properties. Most high-speed filling machines are equipped with a hot hydrogen peroxide sterilizing system to sterilize the packaging film. Hydrogen peroxide has strong oxidizing properties, and its oxidizing property is significantly increased with the increase of temperature, which is an anti-oxidation capability for printing inks. Put forward higher requirements. If the oxidation resistance of the pigment in the ink is not good, ink fading occurs and the product quality is affected.
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