Seven cases of milk packaging film printing failure

In the printing production of milk packaging films, various problems often arise. The following is a summary of the solutions to these problems and I hope to help everyone.


Problem I: Reasons for poor adhesion of ink

(1) The film material has low surface tension and poor wettability with the ink.
(2) An excessive amount of slip agent is added to the film during the blowing process to reduce its surface tension.
(3) Additives in the film (plasticizer, slip agent, etc.) migrate to the surface to form a weak interface layer.
(4) The surface of the film is not clean, and foreign matter such as grease, dust, etc. is adhered.
(5) The quality of the ink itself is poor, the affinity to the plastic film is poor, or the ink has deteriorated.
(6) Insufficient ink drying, more residual solvents.

Solution:
(1) Renew plastic film and perform corona treatment on the film.
(2) Replace the plastic film to ensure proper control of the amount of lubricant added during the blown film process.
(3) Clean the surface of the plastic film to remove oil and dust on the film surface.
(4) Replace the ink.
(5) Properly reduce the printing speed, increase the drying temperature, and ensure that the ink is fully dried.

Problem 2: Causes of Printing Film Adhesion Problems

(1) The film material has a low level of slip agent and is inherently tacky.
(2) The ink is sticky and the softening point of the binder resin is too low.
(3) The ink is not completely dried and some of the solvent is not evaporated. After the printing film is left for a period of time, the residual solvent continues to infiltrate.
(4) The printed film is directly wound without being cooled sufficiently.
(5) The winding tension is too large.
(6) The temperature and relative humidity in the workshop or warehouse are too high.

Solution:
(1) Replace the film substrate material.
(2) Replace the ink.
(3) Properly reduce the printing speed, increase the temperature of the drying oven, and increase the air volume so that the ink can be thoroughly dried.
(4) The printed film must be fully cooled by the chill roll and then rewinded.
(5) Under the premise of ensuring that the winding is neat, the winding tension should be reduced as much as possible, and the winding diameter should not be too large.
(6) Pay attention to the control of the temperature and relative humidity in the workshop.

Problem 3: Causes of odor problems in the printed film

(1) Add some odorous auxiliaries to the film production process.
(2) The printing speed is too fast, the strength of the drying system is insufficient, the ink is not fully dried, and more solvent remains in the film.
(3) In the printing process of plastic film, a large amount of high-boiling, odorous solvent is added to the ink, and the solvent is still left in the film after it is not completely dried.

Solution:
(1) Replace the plastic film.
(2) Reduce the printing speed and fully ventilate to ensure that the ink is fully dried.
(3) Do not use or use odorous, odorous high-boiling solvents.

Problem 4: Causes of Blooming Problems in Printing Films

(1) The film is stored for a long time or the film has a high level of slip agent.
(2) The temperature of the warehouse or printing shop is too high and the migration of the slip agent is intensified.

Solution:
(1) Replace the film material.
(2) Control the temperature and humidity control of warehouses and printing shops to ensure good ventilation.

Question 5: The reason for overprinting is not allowed

(1) The thickness of plastic film is not uniform, such as lotus leaf, thick and thin.
(2) The drying temperature of the printing press is too high or the strength of the hot air drying system is too high.
(3) Improperly set the tension on the printing press.

Solution:
(1) Replace the polyethylene film with a smaller expansion ratio.
(2) Replace the thick and uniform polyethylene plastic film.
(3) Properly increase the printing speed, reduce the temperature of the drying oven, and minimize unnecessary hot air drying.
(4) Adjust the tension setting of the press.

Question 6: Causes of biting problems

(1) The first color ink dries too slowly.
(2) The second color printing pressure is too high.
(3) The printing speed is too fast.

Solution:
(1) Accelerate dry solvents in the first color ink, increase ventilation and oven temperature for the first color ink.
(2) Reduce the printing pressure of the second color appropriately.
(3) Reduce printing speed appropriately.

Question 7: Causes of poor heat sealing performance of milk film

(1) Recycled recycled material is mixed when blowing polyethylene film.
(2) The blow-up ratio and the draw ratio are too large during the blown film process, resulting in poor film heat-sealing performance.
(3) The dew point line is too low, causing the molecule to undergo transverse stretching orientation.
(4) Extrusion temperature is too high when the film is blown, causing the heat sealability of the film to decrease.
(5) The content of slip agent in the film is too high, which affects the heat-seal fastness of the film.

Solution:
(1) Blow the film back with new material.
(2) The blow-up ratio and the traction ratio are appropriately smaller, generally controlled between 1.5 and 2.
(3) The dew point line is controlled a little higher so that inflation and traction are performed as far as possible at the melting point of the polyethylene resin.
(4) It is advisable to reduce the extrusion temperature appropriately, generally between 1600C and 1800C.
(5) Appropriately reduce the amount of the slip agent in the blown film process.

Source: hc360 HC Printing Industry Channel