Reasons and Countermeasures for Poor Heat Sealing of Paper-Plastic Packaging Bags
Reason:
(1) The adhesive in the composite film has not yet fully hardened.
(2) improper heat sealing conditions.
(3) The distance between the heat sealing knife and the cooling knife is too long.
(4) There is a problem with the inner seal film.
(5) The poor heat resistance of the ink leads to the reduction of the composite strength of the film at the heat-sealed part.
(6) Dust, dusting and other substances are attached to the hot cover.
(7) The composite strength is low or the composite strength at the heat seal decreases too much.
Countermeasures:
(1) The curing (curing and curing) of the adhesive is promoted through heat preservation and aging to improve the composite strength and heat resistance of the composite film.
(2) Select the best heat-sealing conditions (temperature, time and pressure) according to the structure and heat-sealing state of the composite film, or improve the heat-sealing method, and cool immediately after heat-sealing.
(3) Check the shelf life and preservation conditions of the heat-seal layer film. If the heat-seal layer uses old batch number films and heat-seal processed films, special attention should be paid.
(4) increasing the thickness of the heat-sealing layer film.
(5) Change the type and grade of heat seal film and use the inner seal film with anti-pollution heat seal property.
(6) Check whether the grade of the adhesive meets the requirements (exudation of low molecular substances in the resin may sometimes affect the composition of the adhesive).
(7) Improve the heat-sealing performance of the heat-sealing layer (substrate), control the content of smooth agent, and adopt LLDPE film.
(8) controlling the monomer content of MDI in the composite adhesive.
(9) Check the treatment degree of hot cover.
(10) Change the ink (preferably two-liquid ink).
(11) Change the printing pattern of the packaging bag so that the part printed with ink avoids the heat-sealing part, or change the heat-sealing method. (Pay special attention to metallic ink not to be printed on the seal).
