Bag making processing is a process in the production and processing of plastic flexible packaging. If the quality of the bag is not up to standard or the consumption is too high, it may be equivalent to the complete abandonment of the previous processes, and in severe cases, downstream customers may claim compensation and have a significant impact on the production and operation of the enterprise.

Heat sealing is the result of the combined action of heat and force. On the one hand, in the molten state of the sealing surface, large molecules diffuse, penetrate, and entangle with each other, achieving sealing sealing; On the other hand, the polymer molecules in the molten state rely on the pressure of the heat sealing tool to fuse the upper and lower layers of thin films into one, which can maintain a certain strength after cooling and shaping.

The quality of bag making and heat sealing in composite packaging bags has a significant impact on various aspects such as packaging process, transportation, storage of contents, and product distribution. The following are the common problems and solutions that may arise during the bag making process.

1. Incomplete heat sealing can cause leakage or deterioration of the contents.

Reason: The anti pollution heat sealing performance of the film is poor, mainly due to the inappropriate resin used in the inner sealing layer.

Countermeasure: Use thin films with good anti pollution and heat sealing properties. Generally speaking, LDPE has moderate anti pollution heat sealing properties, EVA has good anti pollution heat sealing properties when the VA content is high, LDPE also has good anti pollution heat sealing properties, while ionic resins and metallocene polymers have good anti pollution heat sealing properties.

2. Sealing becomes brittle and brittle.

Reason:

(1) The heat sealing temperature is too high.

(2) Excessive pressure.

(3) The heat sealing time is too long.

(4) The edge of the upper sealer is too sharp or the wrapped polytetrafluoroethylene is damaged.

(5) The silicone rubber at the bottom seal is too hard.

(6) During the compounding and maturation process, a portion of the adhesive penetrates into the interior of the film. Due to the penetration effect of the adhesive, the toughness (impact resistance) of the substrate decreases and the brittleness increases.

(7) After cooling and placing, the heat sealing strength of plastic composite packaging bags increases, and there is also a tendency to become brittle.

Countermeasures:

(1) Select the appropriate processing temperature, pressure, and heat sealing time based on the heat sealing characteristics of the inner sealing layer material.

(2) Improve the surface condition of the upper heat sealing knife to make the surface of the sealer flat.

(3) Wrap with polytetrafluoroethylene cloth intact.

(4) Choose a silicone rubber pad with appropriate hardness.

3. The outer contour of the heat sealed surface is unclear. (Unclear blade pattern)

Reason:

(1) Short cooling time.

(2) Poor contact of the cooling plate.

(3) Due to the heating of the silicone pad, the edges melted.

(4) The longitudinal heat sealing force is uneven.

(5) The edge of the heat sealing knife is uneven and dull.

Countermeasures:

(1) Adjust the cooling time.

(2) Adjust the cooling plate.

(3) Replace or adjust the heat sealing knife.

(4) Prevent edge melting caused by silicone pad overheating.

4. The bag warps after heat sealing.

Reason:

(1) The thickness of the composite film is inconsistent.

(2) The heat sealing temperature is too high or the heat sealing time is too long.

(3) In the longitudinal heat sealing blade section, the running trajectory of the composite film is uneven.

(4) Insufficient cooling.

(5) Insufficient maturation time.

(6) The surface substrate film has poor heat resistance.

(7) Improper tension matching control of the composite substrate during the composite process leads to residual stress after aging and shaping, especially when the composite film thickness is thin, which is more prone to such faults.

Countermeasures:

(1) Adjust the tension of the floating roller.

(2) Select inner sealing substrate with low-temperature heat sealing properties.

(3) Adjust the heat sealing temperature to the appropriate temperature.

(4) Adequate cooling.

(5) Fully ripen.

(6) Re select the surface substrate film.

(7) Adjust the tension of each part of the composite processing equipment to ensure that the shrinkage rates of the two composite substrates are equal as much as possible.