2、 Friction coefficient problem
Friction in packaging is often both drag and resistance, so its size should be controlled within an appropriate range. Coils for automatic packaging are generally required to have a small internal friction coefficient and a suitable external friction coefficient. Too large external friction coefficient will cause excessive resistance in the packaging process, causing material stretching deformation. If it is too small, it may cause the drag mechanism to slip, causing inaccurate tracking and cutting positioning of the electric eye. However, the friction coefficient of the inner layer should not be too small. If the friction coefficient of the inner layer of some packaging machines is too small, the stacking of materials will be unstable during bag making and molding, resulting in misalignment; For the composite film for strip packaging, too small friction coefficient of the inner layer may also cause slipping of the tablet or capsule, resulting in inaccurate positioning of the blanking. The friction coefficient of the inner layer of the composite film mainly depends on the content of the opening agent and the smoothing agent of the inner layer material, as well as the stiffness and smoothness of the film. The corona treated surface, curing temperature and time during the production process also affect the friction coefficient of the product. When studying the friction coefficient, special attention should be paid to the great influence of temperature on the friction coefficient. Therefore, it is not only necessary to measure the friction coefficient of packaging materials at room temperature, but also to investigate the friction coefficient at the actual use environment temperature.
3、 Heat sealing problem
The low temperature heat sealing performance is mainly determined by the performance of the heat-sealing resin, and it is also related to the pressure. Generally, the extrusion temperature is higher when extruding and compounding, and the low temperature heat sealing performance of the material will be reduced if the corona treatment is too strong or the film is parked too long. Thermal viscosity is used to describe the peeling strength of the melting surface of the heat seal layer against external force when it is not fully cooled and solidified after heat sealing: this external force often occurs in the automatic filling packaging machine. Therefore, the composite film coiled material used for automatic packaging should be the heat-sealing material with good thermal viscosity. Pollution resistance heat sealing, also known as inclusion content heat sealing, refers to the performance of heat sealing when the hot surface adheres to the content or other pollutants. The composite film selects different heat-sealing resins according to different packaging materials, packaging machinery and packaging conditions (temperature, speed, etc.). One heat sealing layer cannot be used uniformly. Low temperature heat sealing materials shall be selected for packages with poor heat resistance. For heavy packaging, heat sealing materials with high heat-sealing strength, high mechanical strength and good impact performance shall be selected. For high-speed packaging machines, low temperature heat sealing materials and heat-sealing materials with high thermal viscosity strength shall be selected. For products with strong pollution such as powder and liquid, heat sealing materials with good pollution resistance shall be selected.
Post time: Feb-04-2023