For aluminum foil packaging, the quality is largely reflected in the heat sealing strength of the product.Therefore, several factors that affect the heat sealing strength of aluminum foil bags become the key to improve product packaging quality.
1. Raw and auxiliary materials
The original aluminum foil is the carrier of the adhesive layer, and its quality has great influence on the heat sealing strength of the product.
On the one hand, the oil stain on the surface of the original aluminum foil will weaken the adhesive force between the adhesive and the original aluminum foil.If there is oil stain on the surface of the original aluminum foil and the surface tension is lower than 31×10-3μm, it is difficult to achieve the ideal heat seal strength.On the other hand, the insufficient metal composition and surface brightness of the original aluminum foil affect the strength of heat sealing, and the quality of the original aluminum foil must be strictly controlled.
Adhesive is a special substance containing solvent. Under certain technological conditions, it is coated on the dark side (or smooth side) of the original aluminum foil and dried in a drying tunnel to form an adhesive layer, which plays a decisive role in the heat sealing strength of the product.
At present, most domestic manufacturers use imported raw materials to prepare adhesives, and the products can achieve higher heat sealing strength.However, imported raw materials are too expensive. In order to obtain high profits, some manufacturers with strong scientific research strength have started to research and develop domestic similar raw materials.
3. Production technology
Under the control of certain technological parameters, the adhesive is coated on the surface of the original aluminum foil to form a film, and the quality of the finished composite film will directly affect the heat sealing strength of the product.Among them, the more important parameters include the coating speed, the section temperature of the drying tunnel, the pattern shape, depth, line number of the coating roller, and the position and angle of the scraper.
The coating speed determines the drying time of the coating in the drying tunnel.If the coating speed is too fast and the oven temperature is too high, the solvent on the surface of the coating film will volatilize too fast, resulting in the residue of solvent in the film. The coating film will not dry sufficiently and it is difficult to form a dry, firm and firm adhesive layer. This will definitely affect the heat sealing strength of the product and cause adhesion between the product layers.
The shape, depth, number of lines and the position and angle of the doctor blade of the coating roller determine the thickness and uniformity of the coating film.If the selection or adjustment is not appropriate, the adhesive cannot be evenly coated on the surface of the original aluminum foil, resulting in uneven film formation, and the heat sealing effect of the product will not be good and the strength will also be affected.
4. Heat sealing temperature
Heat sealing temperature is an important factor affecting heat sealing strength.If the temperature is too low, the adhesive layer cannot be well heat sealed with PVC film, and the adhesion between the adhesive layer and PVC film is not firm.If the temperature is too high, the drugs will be affected.Therefore, a reasonable heat sealing temperature is usually between 150℃ and 160℃.
5. Heat sealing pressure
To achieve the ideal heat sealing strength, a certain heat sealing pressure must be set.If the pressure is insufficient, not only can the adhesive layer of the product and PVC film not be fully adhered and heat sealed, but also air bubbles can remain between the two, thus achieving a good heat sealing effect.Therefore, the national standard stipulates that the pressure for heat sealing is 0.2×10Pa.
6. Heat sealing time
The heat sealing time will also affect the heat sealing strength of the product.Under normal circumstances, under the same heat-sealing temperature and pressure, a longer heat-sealing time can make the heat-sealing parts sealed more firmly and completely, and can better achieve the expected heat-sealing strength.However, the technological conditions of modern high-speed drug packaging machines cannot provide long time for heat sealing. If the heat sealing time is too short, the heat sealing between the adhesive layer and PVC film will be insufficient.For this reason, the national standard stipulates a scientific heat sealing time of 1s.