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Control points of composite packaging film products

    In recent years, the demand for flexible packaging film products has been increasing, and the proportion has been rising. This is because the customer’s automated production level is gradually improving, and packaging film rolls can reduce labor costs and labor intensity, and improve production efficiency. Therefore, whether it is in the fields of medicines, cosmetics, food, daily chemicals, and industrial fields, the use of packaging film has been increasing. Then I will explain the control points of composite flexible packaging film on three points:

    First. C.O.F (coefficient of friction).

    Second. Product flatness.

    Third. Stretch and shrinkage of roll film products.


First. C.O.F (coefficient of friction)

    Packaging roll film products are required to be smoothly applied to automated packaging equipment. Therefore, the first point of packaging film products is to match the performance of automated equipment. Generally, the most basic requirements for automatic packaging equipment for film rolls are whether the machine can pass the material and whether the drawing is smooth, which involves a key point in the production of roll film-C.O.F (that is, coefficient of friction). The friction coefficient, when we are producing, we often only consider two aspects at present: one is the friction between the packaging film fabric and the fabric, and the other is the friction between the inner layer and the inner layer of the packaging film. When we do the test, we also Only focus on these two friction coefficients. However, if it is to produce roll film, you also need to consider the friction surface of the automatic packaging machine when the customer is actually using it. At this time, it is generally the friction between the surface layer of the packaging film or the inner layer of the packaging film directly in contact with the equipment, and this friction will directly determine its smoothness. At the same time, the friction data we have to pay attention to is the friction coefficient between the inner layer and the outer layer. The size of this coefficient will directly determine the unwinding smoothness of the finished film. If the coefficient of friction is too large, the roll film will not be unrolled too smoothly when the customer uses it. This is the most basic control key point for roll film feeding on automated packaging equipment.



The main factors affecting the friction coefficient


  1. Raw materials.If the coefficient of friction of the raw material itself is very large, it is essentially impossible to reduce the coefficient of friction in this state in subsequent production. But we can increase the smoothness of packaging film by spraying powder. Powder spraying is a way to increase the smoothness from the surface, that is, to reduce the coefficient of friction. But when using this kind of method, we must especially remind that what kind of powder is used, what is the content of the customer’s package, whether there is a certain conflict with the powder, or even a chemical reaction. On the other hand, how to control the amount of powder spraying, spray less, the effect will not be achieved, spray more, it will affect the sealing performance, so this degree must be controlled well.
  2. Curing time.What if the customer needs a less slippery product, that is, a product with a large friction coefficient? This estimate is not too easy to do. Experienced production personnel will also think of a way to increase the curing time to control (this aspect is also one of the links that affect the friction coefficient). This operation seems to be easier to master than dusting. In fact, this is more difficult to grasp: this is because the powder spraying is a visible quantity, and the maturation time is only a time concept, but there is no actual measurement. It can only be known by testing in a certain period of time. In such a process, it is difficult to know whether a whole roll can achieve the effect of improving the coefficient of friction. Therefore, the operation of increasing the curing time will be much more difficult than the operation of spraying powder to reduce the friction coefficient. Therefore, maturation is actually a key point that affects the change of friction coefficient.
  3. Type of glue. The polyurethane glue currently on the market, normally speaking, will not have much influence on PP or PE materials. However, some special glues, such as polyurethane glues containing certain ether components, will have certain chemical and physical reactions with PP and PE slip agents to a certain extent, and most of them will cause the packaging film The smoothness of the layer film is low, that is, the originally slippery film. After compounding with ether polyurethane glue, the friction coefficient will be significantly larger.

Second. Product flatness,

    The flatness of packaging film is generally divided into two aspects.

    First, it refers to the flatness of the packaging film end surface. In this respect, the standard requirement in the national standard is ±2mm, but for those narrow packaging rolls, such as rolls with a width of less than 50mm, then if the flatness really has a deviation of 2mm, the correction requirements for general automation equipment will be compared High, but the most fatal thing is that there are some automatic packaging equipment, there is no correction device at all, the flatness accuracy of the film end face will be higher. Otherwise, the product will basically have an over-range deviation in the automatic packaging process.

    The second aspect of flatness refers to the flatness of the rolled film surface after the film is pulled out (also commonly known as the curling degree of the rolled film product). For this point, general products do not have too high requirements, but this curling It directly affects the packaging effect or efficiency of automatic packaging equipment, and even some automatic packaging equipment has very strict requirements on the curling of this roll film, and the roll film warpage exceeding 30° is regarded as a non-conforming product. The main processes that affect the degree of roll film curl are the compound process (including the control of the curing conditions) and the control of the tension of the slitting itself. In terms of compounding, there will mainly be the matching of winding and unwinding and oven tension. If the optimal state is not reached, it may have a certain impact on general materials, especially the material structure contains BOPA structure, but there is no steel material material. It is very prone to warpage of the roll film.

Third. Material stretching and shrinking

    This is the easiest and most difficult point to control the packaging film products. For example, BOPA/PE material structure, although BOPA material is stretched very well, it is because of its ideal stretchability, it also becomes a weak point of it at the same time, it is easy to be mechanically stretched or contracted at high temperature, or Stretching and shrinking, so this kind of material will be easily stretched and deformed in the printing process, and then stretched and contracted in the composite process, and finally stretched and deformed again on the slitting equipment. In the end, the cursor distance in the customer’s use will be different in length, resulting in unavailability. The stretching deformation of packaging film products is mainly easy to produce in the process of printing, laminating and slitting. Therefore, for products of this kind of material, you need to be very careful in the production process to control the tension coordination of each process period, and The tension system in the machine is matched, otherwise it is easy to cause the product to be scrapped, or even a whole batch of scrap.



    For packaging film products, it is not an easy task to do a good job. The main control points involved include COF (coefficient of friction), product flatness, and stretch shrinkage of film products. After solving these problems , I believe that most products can be suitable for most automatic packaging equipment and become the competitive advantage of enterprises.

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