Relationship between hot tack force and filling efficiency of packaging materials

The heat sealing performance of packaging materials is the main indicator to evaluate the packaging performance of materials, including hot tack and heat sealing strength. The peeling force of the heat sealing part of the material in a short time (not yet cooled) after the heat sealing is the hot tack of the material. Hot Tack, while the Ultimate Strength is the peel strength of the fully sealed part of the heat seal, the two indicators of the same material are very different. However, in fact, the good application of these two indicators is often directly related to the choice of packaging materials and the actual filling efficiency. This paper uses the packaging material selection of the filling production line as an example to introduce the application of the material's hot tack and analysis and evaluation.

1. Use of hot tack

Today, most form-fill-seal machines are used for soft pack filling in food, medicine, cosmetics, and other fields. In these filling production lines, the production process and filling process of flexible packaging bags are carried out at the same time, and the product filling method is basically that the products fall into the packaging bag from a certain height and have a strong impact on the bottom of the packaging bag. The bottom of the bag can not withstand the impact of the role of the bottom crack will appear - broken bags, not only will affect the cleanliness of the production environment, but will affect the filling efficiency. Due to the very short interval between the two-step operation of heat-sealing the bag and the filling of the filling line, it is not possible to completely cool the heat-sealing part of the bag within such a short time interval. The heat seal strength is not suitable for the evaluation of the heat sealing properties of the material. The hot tack of the material should be used. Optimizing the heat sealing process in the packaging process has been widely recognized as an effective way to shorten the packaging cycle time, and the hot tack detection can help the operator to select the optimal heat sealing parameters.

Therefore, the difference between the application of hot tack force and heat seal strength is very clear. The hot tack property is used to ensure the normal operation of the filling production line. Its suitability directly affects the filling efficiency and bag breaking rate; and the heat sealing performance It is mainly used to evaluate the storage performance of materials and ensure that the heat-sealing part does not leak during transportation, storage and display. It is the premise of realizing the functionality of packaging materials.

2. Case study

How to choose the best production line heat sealing parameter by testing the thermal tack of the material? The following takes the customer test entrustment accepted by Labthink Lab as an example to introduce the relationship between the hot tack force and the selection of the heat sealing parameters of the production line.

The customer is a food production company in Southeast Asia. He wants to choose one of the two types of A and B films with similar performance indexes to meet the requirements of the production line and to make the production line with higher filling efficiency. Affected by other factors, the hot-sticking time and heat-seal pressure that the production line can provide have been determined, and the thermal cover of the material is also determined. The customer requires that the heat-sealing temperature of packaging materials is not higher than 133°C and the hot-sticking force is not less than 2N. The heat-sealing time should be as short as possible on the basis of meeting the above requirements, and the principle of energy-saving should be taken into consideration.

We used Labthink HTT-L1 thermal tack tester to measure the thermal tack of A and B films. The heat sealing time was set to 0.3s, 0.5s, and 0.7s. The heat sealing temperature was set to 115°C, 118°C, 121 °C, 124 °C, 127 °C, 130 °C, 133 °C, other indicators set in accordance with customer requirements, test specimen width in accordance with customer requirements to be taken as 25mm. Figures 1 and 2 are test data curves.

Figure 1. Film A: Diagram of Hot Tack Force versus Sealing Temperature and Sealing Time

Figure 2. Film B: Hot Tack Force vs. Sealing Temperature and Sealing Time

In fact, there is a most suitable temperature point for achieving the best hot tack of the film material, and the hot tack temperature will show a decreasing tendency when the heat sealing temperature exceeds this temperature point. From Fig. 1 and Fig. 2, we can see that the optimum heat-sealing temperature of film A is about 130°C, and the best heat-sealing temperature of film B is about 127°C.

For data analysis, for film A, when the heat sealing time is 0.3 s, the thermal adhesive force does not meet the customer's requirements; when the heat sealing time is 0.5 s, the heat sealing temperature is between 127° C. and 133° C. The hot tack force can just meet the customer's requirement; when the heat sealing time is 0.7s, the hot tack temperature of the material in the range of 127°C~133°C can meet the requirements well. Therefore, for the film A, only when the heat-sealing time is more than 0.5s and the heat-sealing temperature is between 127°C and 133°C can meet the customer's requirements for the thermal adhesion of the material. The film B shows much better thermal adhesion than the film A with the same heat-sealing parameters. When the heat-sealing time is not less than 0.3s, the heat-sealing temperature is between 118°C and 133°C. Adhesion requirements; and with the increase in sealing time, the required sealing temperature significantly decreased, when the sealing time increased to 0.7s, the sealing temperature at any temperature point in the 115 °C ~ 133 °C, the film B are To meet customer requirements.

With reference to the above test data, we believe that the film B should be used. The heat sealing parameters of the production line can be set to: the heat sealing time is 0.3 s ~ 0.5s, and the heat sealing temperature is 118°C. Of course, the heat sealing temperature point should also be determined through further tests to determine the best value, but pay attention to the thermal adhesive force should be left with a certain margin, in order to avoid heat sealing due to heat sealing mechanism factors or material factors caused by non-uniform heat sealing caused by insufficient strength The problem. From the material analysis alone, we believe that the use of A sample will reduce the filling efficiency and increase the energy consumption of the production line. However, further data analysis should also consider the cost of packaging materials and the best working efficiency of the entire production line.

3. Summary

In order to reasonably set the heat sealing process parameters of the filling line, the thermal adhesion of the material should be mainly considered. Using the thermal tack tester, we can adjust the heat sealing time, hot tack time, heat sealing temperature and heat sealing pressure at will, and analyze the best parameter combination mode from the test data chart and the actual situation of the production line. Of course, material costs should also be taken into account in order to achieve the optimization of production costs and production efficiency.