Counting 90% of bag making mistakes made by flexible packaging plants

【Chinese Packaging Network News】 Bag-making process is the last process of plastic flexible packaging production and processing, if the bag quality is unqualified or the consumption is too high, then the weight is equal to the previous several processes before the work is abandoned, while the weight is to the customers' claims. The production and operation have a significant impact.

1. What should I do if the heat sealing of the bag making machine does not completely result in leakage or deterioration of the contents?

Cause: The anti-fouling heat sealability of the film is poor, mainly because the resin used in the inner seal layer is not suitable.

Countermeasures: Use anti-pollution heat-sealing film. In general, LDPE has a moderate anti-pollution heat sealability, EVA has a good anti-pollution heat sealability when the VA content is large, LDPE also has a good anti-pollution heat sealability, ionic resin and metallocene polymer Has excellent anti-pollution heat sealability.

2, bag making machine sealing crisp and brittle broken how to do?

Reasons: (1) excessive heat seal temperature; (2) excessive pressure; (3) excessive heat sealing time; (4) sharp edge of upper sealer or damage of coated PTFE; (5) ) Silicon rubber at the bottom is too hard; (6) During compounding and curing, a portion of the adhesive penetrates into the interior of the film. As the substrate is affected by the penetration of the adhesive, the toughness (impact resistance) is reduced and the brittleness is improved; (7) After the plastic packaging bag is cooled and placed, the heat sealing strength is increased, and there is a trend of becoming brittle. .

Countermeasures: (1) According to the heat sealing properties of the material of the inner seal layer, select the appropriate processing temperature, pressure and heat sealing time; (2) improve the surface condition of the upper heat seal knife, and make the surface of the sealer flat; (3) to gather Tetrafluoroethylene cloth is well-wrapped; (4) Choose a silicone rubber pad with suitable hardness.

3, how to do when the bag is warped after heat sealing?

Reasons: (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 knife part, the running path of the composite film is not straight; (4) Cooling is not Full; (5) insufficient curing time; (6) poor heat resistance of the surface layer substrate film; (7) improper control of the tension matching of the composite substrate in the composite process, resulting in residual stress after maturation and setting, especially Thinner composite films are more prone to such failures.

Countermeasures: (1) adjust the tension of the floating roller; (2) select the inner sealing substrate with low-temperature heat-sealability; (3) adjust the heat-seal temperature to a suitable temperature; (4) fully cool; (5) fully mature (6) Reselect the surface layer film; (7) Adjust the tension of each part of the composite processing equipment to make the recombination rates of the two composite substrates equal as far as possible.

4. What should I do if the outline of the heat seal surface is not clear? (The knife pattern is not clear)

Reasons: (1) short cooling time; (2) poor cooling plate contact; (3) melting of the edge due to heating of the silicone pad; (4) uneven horizontal heat sealing force; (5) edge of the heat sealing blade is not Neat and blunt.

Countermeasures: (1) Adjust the cooling time; (2) Adjust the cooling plate; (3) Replace or adjust the heat-sealing knife; (4) Prevent the edge melting caused by the overheating of the silicone pad.

5, how to do bad heat seal?

Causes: (1) The adhesive in the composite film has not been hardened sufficiently; (2) The heat seal condition is not appropriate; (3) The distance between the heat seal knife and the cooling knife is too long; (4) There is a problem with the inner seal film. (5) The heat-resistant sealability of the ink is poor, resulting in a decrease in the composite strength of the film at the heat-seal site; (6) Dust, dusting and other substances adhere to the thermal cover; (7) The composite strength is low or the composite strength at the heat-sealing site is decreased excessive.

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Countermeasures:

(1) Hardening of the binder (curing, curing) by heat aging improves the composite film's composite strength and heat resistance.

(2) Select the best heat sealing conditions (temperature, time, and pressure), or improve the heat sealing method according to the composition of the composite film, the heat sealing state, etc., and cool immediately after heat sealing.

(3) Check the shelf life and storage conditions of the heat seal layer film. If the heat seal layer uses an old batch film and a heat seal film, pay special attention.

(4) Increase the thickness of the heat seal layer film.

(5) Change the type and grade of the heat seal layer film, and use an inner seal layer film with anti-contamination heat sealability.

(6) Check whether the quality of the adhesive meets the requirements (the exudation of low-molecular substances in the resin sometimes affects the composition of the adhesive).

(7) To improve the heat sealing performance of the heat seal layer (base material) and to control the content of the lubricant, the mLLDPE film was used.

(8) Control the monomer content of MDI in the adhesive binder.

(9) Check the extent of the thermal cover.

(10) Replace the ink (preferably two-liquid ink).

(11) Change the printing pattern of the packaging bag so that the ink-printed portion avoids the heat-sealing portion or changes the heat-sealing method. (Special attention should not be printed on the metal ink seal).