Control Points of Composite Flexible Packaging Roll Film Products
Abstract: This article introduces the key process control points in the production process for roll film products to meet the performance requirements of automated packaging equipment.
In the consciousness of many flexible packaging enterprises, the ROLL FILM PRODUCT is a very simple, not much technical content of the product, and for some ordinary and undemanding roll film products, the production is really very simple. But it's also a product with less competitiveness, because everyone can do it, and there's no special points of control. Therefore, this kind of product has already fallen into the price war.
To producing the same roll film product, if it is positioned on the high-end, it may be able to improve the competitiveness of the products.
1. Requirements of high-speed automatic packaging equipment on roll film products
Roll film products are generally applied to automatic packaging equipment instead of manual packing. Therefore, the first point of the roll film products is to match the performance of automation equipment.
Generally, the most basic requirement of automatic packaging equipment for roll film is whether the materials can be feed smoothly on the machine, which involves a key point in film production -C.O.F(friction coefficient).
When we produce, we often only consider two aspects of the friction coefficient:
One is the friction between the surface layers, and the other is the friction between the inner layers of the roll film. When we did the test, we only focused on these two friction coefficients. But for the production of roll film, it is also necessary to consider the actual use of customers, the friction surface of the automatic packaging machine when feeding. At this time, it is mainly the friction between the surface layer or the inner layer of the film directly and the equipment, which will directly determine the smoothness of its feeding.
At the same time, we also need to focus on the friction coefficient between the inner and outer layers. The value of this coefficient will directly determine the unwinding smoothness of the finished film. If this value is rather big, the roll film will not be too smooth when the customer uses it. This is the most basic control key point of the roll film when it is feed in the automatic packaging equipment.
2. The main factors affecting the friction coefficient
(1) Raw materials
If the friction coefficient of the raw material itself is very large, then in the subsequent production, it is basically impossible to reduce the friction coefficient in this state. But we can increase the smoothness of the film by spraying powder, which is a way to increase the smoothness of the surface, that is, to reduce the coefficient of friction. However, when using such methods, it is special to remind that what kind of powder is used, what is the content of the customer's packaging, and 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, spray less, the effect can not reach, spray more, it will affect the sealing performance, so we must make sure to use it in a right way.
(2) Curing time
What if the customer needs something less slippery, that is, something with a high friction coefficient, which is not easy to do either.
Experienced production personnel will also think of a way to control it by increasing the curing time, which is also one of the links to affect the friction coefficient. This operation seems to be easier to master than powder spraying. The truth is, the curing time is harder to control. That’s because we can control the use amount of the powder when spraying; but it is hard to determine the curing time since there is no actual measurement. You can only know if you test it at a certain time. In such a process, it is difficult to estimate whether the whole roll of film can achieve the effect of improving the friction coefficient. So the operation of increasing the curing time will be much more difficult than the operation of powder spraying to reduce the friction coefficient. Therefore, curing is also a key point that affects the change of friction coefficient.
(3) Glue type
At present, the polyurethane vinegar glue on the market, normally, for PP or PE materials will not have much impact. However, there are some special glue, such as polyurethane vinegar glue containing certain ether components, which will react with PP and PE materials to a certain extent. Most of them will lead to a low degree of smoothness of the inner film, which is the original slippery film. After the compound of polyurethane glue containing ether, the friction coefficient will be significantly larger.
3. Precautions for the use of roll film
In the automatic packaging machine, the direction and the flatness of the roll film will affect the smooth feeding of the automatic packaging machine.
(1) Direction of the roll film
The direction needs to be divided into vertical direction, that is the mechanical direction. According to the current equipment, this direction is not a big problem. But, we also know that, customers do not often change the conventional settings once the equipment is set up, for example, the coding position, coding direction and the middle seal direction. So once the vertical direction is opposite, the customer will generally reject to accept the goods.
On the other hand, it refers to the direction of the surface layer and the inner layer, which does not usually go in wrong direction. However, there are some products we are easy to ignore, which leads to the wrong direction, such as blank film. Sometimes, in order to control the tension of the winding, the heat sealing layer is received outside, and when cutting, if you do not notice, it is easy to make it the wrong vertical direction.
(2) Flatness of the roll film
Generally, there are two main aspects: Firstly, it is the flatness of the end surface of the film. In this regard, the national standard requires deviation of ±2mm. But for those narrow film, such as the width of film is less than 50 mm, if the flatness deviation is really ±2mm, it has higher requirement on the correction device of the general automatic equipment. The worst of it is, some automatic packing equipment has no correction device, which has higher requirements on the flatness of the end surface of the film; Otherwise, the product will basically exist out-of-range deviation in the automatic packaging process.
Secondly, it refers to the flatness of the film surface after pulled out (also known as the crimpness of the roll film). For this point, the general product does not have too high requirements, but this flatness will directly affect the packaging result and efficiency, even some automatic packing equipment has strict requirements on this crimpness. The roll film with warpage of over 30°is regarded as unqualified products. The crimpness of the roll film will mainly affect the process of laminating process (including control of the cure conditions) and the tension control of cutting. During the laminating process, there will be the matching of winding and oven tension. If it does not reach the best state, there may be some influence on general materials, especially when the material structure contains BOPA structure, but no steel material, it is very easy to appear warpage of the film.
(3) Stretch and shrink of materials
The stretch and shrink of the roll film is easy to happen and one of the difficult control points.
Taking BOPA/PE material structure as an example, BOPA has good tensile strength, which also becomes a weakness, because it is easy to be mechanical stretch or high temperature shrinkage. Therefore, this kind of material will be easily deformed by stretching in the printing process, as well as deformed by shrinking during laminating process, finally, it is stretched and deformed again on the cutting equipment. So that, the cursor distance will be different in use by customers, as a result, it cannot be used.
The stretching deformation of roll film products is mainly happened in the process of printing, laminating and cutting. Therefore, for such material, we have to be very careful in the production process, control the tension coordination in each process period, and the tension system matching in the machinery, otherwise it is easy to result in product obsolescence.
4. Conclusion
For roll film, It is not easy to produce a really good product, because it comes down to the main control points, including C.o.F(friction coefficient), flatness, stretch and shrink of the roll film products. But it is believed if we pay more attention to the control points, the majority of roll film products can be suitable for most of the automatic packaging equipment, and become the enterprise's competitive edge.
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Article From: < PACKAGING FOREFRONT>
Author: Yuan Shengyuan
