For aluminum foil pharmaceutical packaging, the quality is largely reflected in the heat seal strength of the product . Therefore, several factors that affect the heat-sealing strength of pharmaceutical aluminum foil bags have become the key to improving the quality of product packaging.
1. Raw and auxiliary materials
The original aluminum foil is the carrier of the adhesive layer, and its quality has a great influence on the heat seal strength of the product.
On the one hand, the oil on the surface of the original aluminum foil will weaken the adhesion between the adhesive and the original aluminum foil. If the surface of the original aluminum foil has oil stains 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 metal composition of the original aluminum foil and the insufficient surface brightness both affect the strength of the heat seal, and the quality of the original aluminum foil must be strictly controlled.
2. Adhesives
Adhesive is a special substance containing a solvent. It is coated on the dark side (or light side) of the original aluminum foil under certain process conditions. After drying in the drying tunnel to form an adhesive layer, it plays a decisive role in the heat seal strength of the product.
At present, most domestic manufacturers use imported raw materials to prepare adhesives, and the products can achieve higher heat seal strength. However, the price of imported raw materials is too expensive. In order to obtain high profits of products, some manufacturers with strong scientific research strength have begun to research and develop similar domestic raw materials.
3. Production process
Under certain process parameters, so that the adhesive coated surface of the aluminum foil forming the original quality of the finished product can directly affect the composite film heat seal strength of the product. The more important parameters include the coating speed, the sectional temperature of the drying tunnel, the shape of the embossing roller, the depth, the number of lines, and the position and angle of the blade.
The coating speed determines how long the coating dries in the tunnel. If the coating speed is too fast and the drying tunnel temperature is too high, the solvent on the surface of the coating film will evaporate too quickly, resulting in the residual of the solvent in the film. The coating film is not sufficiently dry, and it is difficult to form a dry, strong and strong adhesive layer Affect the heat seal strength of the product, so that the product layer to layer adhesion.
The shape, depth, number of lines, and the position and angle of the coating roller determine the thickness and uniformity of the coating film. If the selection or adjustment is not suitable, the adhesive cannot be evenly coated on the surface of the original aluminum foil, resulting in uneven film formation, the heat sealing effect of the product will not be good, and the strength will also be affected.
4. Heat sealing temperature
The heat sealing temperature is an important factor affecting the heat sealing strength. Temperatures too low to make the adhesive layer with good heat sealing PVC film, adhesion between the adhesive layer and the PVC film will be weak. If the temperature is too high, the medicine will be affected. Therefore, the more reasonable heat sealing temperature is usually between 150 ℃ ~ 160 ℃ .
5. Heat sealing pressure
To achieve the ideal heat seal strength, a certain heat seal pressure must be set. If the pressure is insufficient, not only can the adhesive layer of the product and the PVC film be fully adhered to the heat seal, but also the bubbles can be left between the two, and a good heat seal effect cannot be achieved. Therefore, the national standard stipulates that the pressure of the heat seal 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 perfect, and can better achieve the expected heat sealing strength. However, the process conditions of modern high-speed pharmaceutical packaging machines cannot provide a long time for heat sealing. If the heat sealing time is too short, the heat sealing between the adhesive layer and the PVC film will be insufficient. For this reason, the national standard stipulates that the scientific heat sealing time is 1s .
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