For aluminum foil pharmaceutical packaging, the quality is largely reflected in the heat seal strength of the product. For this reason, we need to analyze the factors that affect the heat seal strength of aluminum foil pharmaceutical packaging, which is very necessary to improve the quality of the product.
The adhesive layer (also known as VC layer) of aluminum foil drug packaging has good thermal adhesion, and can be heat-sealed with PVC film under heating conditions (the adhesive strength is the strength of the heat seal, according to GBl2255 --- 90 stipulates to reach 5.88N / 15mm or more), the medicine in the blister of the treated PVC film can be completely sealed. This adhesive force is not affected by temperature and humidity during long-term storage, and can maintain the efficacy of the drug well and is easy to carry.
The factors that affect the heat sealing strength of aluminum foil pharmaceutical packaging include the following aspects:
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. In particular, the oil stain 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, so the quality of the original aluminum foil must be strictly controlled.
In addition, during the production process, it was found that certain batches of original aluminum foil with technical specifications in all aspects were coated with adhesive under the condition that all process conditions remained unchanged, but the heat seal strength of the final product did not reach The reason is because the metal composition of the original aluminum foil and the surface brightness are not enough. The results of the study show that by changing a special link to make full use of the original aluminum foil, the product has reached the ideal heat seal strength.
2. Adhesive
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. The drying layer is dried to form an adhesive layer, which is decisive for the heat seal strength of the product effect. The adhesive can be divided into colorless transparent, gold and color series, which can be selected according to the needs of users. The adhesives with different compositions have different heat seal strengths in the final products. Most domestic manufacturers use imported raw materials to prepare adhesives, and the products can achieve high 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. This kind of research direction is very tempting. If it can succeed, it will bring huge benefits to the enterprise. It is understood that due to the limited process of domestic raw material manufacturers, domestic raw materials cannot largely replace imported raw materials. If used improperly, it will seriously affect the heat seal strength of the product.
3. Production process
Under the control of certain process parameters, the adhesive is coated on the surface of the original aluminum foil to form a film, and the quality of the film will directly affect the 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 volatilize too quickly, resulting in the residual of the solvent in the film. The coating film is not sufficiently dried, and it is difficult to form a dry, strong and strong adhesive layer. Will affect the heat sealing strength and degree of the product, so that the product layer will adhere to each other.
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 uniformly 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. According to the provisions of the national standard adhesive layer coating, the difference should be less than ± 12.5%. Therefore, it is necessary to strictly follow the parameters specified in the process to complete the process of coating the adhesive layer to form a film to ensure uniform and strong film formation.
4. Heat sealing temperature
The heat sealing temperature is an important factor affecting the heat sealing strength. The temperature is too low to allow the adhesive layer to be heat-sealed well with the PVC film, and the adhesion between the adhesive layer and the PVC film is not strong. 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 not enough, not only can the adhesive layer of the product and the PVC film be fully adhered to the heat seal, but also the bubbles will be left between the two, and a good heat seal effect cannot be achieved. Therefore, the national standard stipulates that the heat sealing pressure 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 specifies a scientific heat sealing time of 1s.
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