How to judge the quality of liquid packaging film

      Liquid packaging film refers to the packaging film of soy sauce and vinegar, which can resist acid, alkali and; Medium hit, usually produced by mixing LLDPE, LDPE, EVA and color masterbatch. Common Faults And Countermeasures Of Liquid Packaging Film Printing

       To judge whether a liquid packaging film is good or not, there are the following requirements:Common Faults And Countermeasures Of Liquid Packaging Film Printing

     The static and dynamic friction coefficient of liquid packaging film should be low, generally controlled between 0.2-0.4, so that it can be filled quickly in a short time on the high-speed filling packaging machine. Common Faults And Countermeasures Of Liquid Packaging Film Printing

      If the friction coefficient is high and the filling speed is low, the filling will be insufficient within a certain time.Common Faults And Countermeasures Of Liquid Packaging Film Printing

    The liquid packaging film can only be printed on the surface, with high fastness, can withstand the hot filling of pasteurization, and will not fall off the ink at the temperature of cryopreservation – 20 ℃.Common Faults And Countermeasures Of Liquid Packaging Film Printing

      It shall have sufficient strength to ensure that it will not be pulled under the tension of high-speed automatic filling machine. Generally speaking, this kind of film is single-layer, with a thickness of more than 10s. It is often mixed with LDPE of two brands with high melting index of 4-6g / 10min and low MI < 1g10min, and blown with color final material, or blown with HDPE and color masterbatch. Common Faults And Countermeasures Of Liquid Packaging Film Printing

      The high temperature resistant film must undergo 121 ℃ sterilization treatment, whether it has shrinkage, good heat sealing and other characteristics. Therefore, it is necessary to correctly select ink and color masterbatch. In the formula, if the resin is too sticky, the melt resin will stick to the fusion sealing knife edge during fusion sealing; If too much smoothing agent is used in the formula, the fusion sealing strength is not high and it is easy to open color.Common Faults And Countermeasures Of Liquid Packaging Film Printing

Ink fastness is not good, easy to decolorize

Factors leading to low ink adhesion of liquid packaging film include:

      The corona treatment of the substrate is less than 40 dyne / cm, and the surface is dense, smooth and has poor affinity with the ink.

     . The addition of oily materials in the color masterbatch is not enough. Although the gloss is improved and the friction coefficient is reduced, the printing fastness and heat sealing fastness are reduced. Common Faults And Countermeasures Of Liquid Packaging Film Printing

      Therefore, the selection of color masterbatch is very important. Improve the adhesion fastness between ink and printing substrate, and strengthen the compatibility between binder in ink and printing substrate film. Select the solvent with good swelling or solubility to the printing substrate film, increase the content of binder in the ink, and add the amount of tackifying resin in the ink to improve the adhesion of the ink.Common Faults And Countermeasures Of Liquid Packaging Film Printing

3. The added solvent is out of balance and does not meet the actual standard.

4. The ink is too old and has impurities, which must be filtered.Common Faults And Countermeasures Of Liquid Packaging Film Printing

5. The added solvent contains water.Common Faults And Countermeasures Of Liquid Packaging Film Printing

The liquid packaging film makes a noise during printing and adheres after winding

       After intaglio winding, the plastic film is divided and cut into packaging bags. After stacking, the ink between the printing surfaces or the ink and the printed blank surface are adhered together and cannot be separated (pulling hard will cause the ink to fall off and the product will be scrapped). Common Faults And Countermeasures Of Liquid Packaging Film Printing

      It should be analyzed from the possible causes of adhesion, that is, the ink is sticky, the humidity is too high, the pressure is too high and so on.Common Faults And Countermeasures Of Liquid Packaging Film Printing

1. Internal factors causing adhesion: the ink itself has poor heat resistance and certain viscosity.Common Faults And Countermeasures Of Liquid Packaging Film Printing

       When a large amount of solvent remains in the printing ink, it is like the phenomenon of wet paint – although it seems dry to the naked eye, it is actually wet and sticky. After the printed matter is rolled up, the residual solvent is difficult to evaporate, and the resin in the ink can not be dried and solidified, resulting in serious adhesion of the finished product.Common Faults And Countermeasures Of Liquid Packaging Film Printing

        For products with adhesion, if determined by gas chromatography, the content of residual solvent often reaches tens of thousands of PPM, and the residual solvent will make the product contain odor. Common Faults And Countermeasures Of Liquid Packaging Film Printing

      This not only affects the composite strength, but also affects the food flavor and hygienic standards. Starting from the performance, drying conditions and load of the dryer; Common Faults And Countermeasures Of Liquid Packaging Film Printing

      Secondly, use fast drying flux as much as possible; Finally, the printing materials should be kept moisture-proof, which is to prevent the moisture in the raw materials from expanding the resin in the ink and producing viscosity.Common Faults And Countermeasures Of Liquid Packaging Film Printing

      The ink is sticky due to improper cost ratio. If special performance (heat resistance and oil resistance) ink is required, hardener shall be added to the ink, and the hardener is a low molecular substance with viscosity. Common Faults And Countermeasures Of Liquid Packaging Film Printing

       The resin has poor heat resistance. In the preparation of gravure ink with synthetic resin, the resin with high global softening point should be selected. Generally, the global softening point is 105 ℃ – the resin softening point between 0 ℃ is too low and heat-resistant.Common Faults And Countermeasures Of Liquid Packaging Film Printing

    The winding is too tight. In the printing process, the film should not be too tensioned or rolled too long or too tight. Because as the printing press does not stop running, the winding is increasing, especially if a local mesh hole is too deep, the area is too large, and it is easy to bulge, adhesion will occur.Common Faults And Countermeasures Of Liquid Packaging Film Printing

      The ink and substrate are not firmly bonded. To solve this problem, we can try from two aspects. On the one hand, we can correctly select the ink and control the quality of the ink to make it adapt to the substrate. On the other hand, the substrate surface should be treated to improve its affinity for ink. Common Faults And Countermeasures Of Liquid Packaging Film Printing

       It is best to deal with one side to eliminate the phenomenon that both sides have good tension. This is because the two-sided electric treatment has too good affinity for the ink surface adhered to, resulting in anti adhesion.Common Faults And Countermeasures Of Liquid Packaging Film Printing

To sum up, when printing milk ink, in addition to correctly selecting the film, we should also fully consider the properties of the ink, such as wear resistance, moisture resistance, temperature resistance, etc.Common Faults And Countermeasures Of Liquid Packaging Film Printing