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In recent years, the demand for flexible packaging laminated roll stock products has been increasing, and the proportion is constantly rising. This is because the automation production level of customers is gradually improving, and roll stock film can reduce labor costs and intensity, and improve production efficiency. Therefore, whether in the fields of pharmaceuticals, cosmetics, food, or daily chemical and industrial industries, the use of roll stock film has been increasing.
While more and more customers are concerning about sustainability. So they are asking for 100% recyclable material for flexible packaging. This means we will need 100% recyclable mono-material PE roll stock products.
In the minds of many flexible packaging companies, roll stock film products are a very simple and low tech product. For some ordinary and low demand products, roll film production is indeed very simple. But this type of product is also a product with little competitiveness, because everyone can do it and there are no control points that need special attention. Therefore, this type of product has long been caught in a price war, and some companies have been operating at a loss in order to win large orders, which is not worth the loss.
If we can position ourselves as high-end producers of roll stock film products, it may give our products better competitiveness. They have requirements of high-speed automated packaging equipment for roll film products. Roll film products are generally not packaged manually anymore, but are used in automated packaging equipment. Therefore, the first key point of roll film products is to match the performance of automated equipment.
As mono-material PE laminated film is more difficult when comparing other conventional non-recyclable material. We will need to do a much better job to make it quality 100% recyclable mono-material PE roll stock film.
There are 6 tips in making quality 100% recyclable mono-material PE roll stock.
The most basic requirement for automatic packaging equipment in terms of film rolling is whether the machine can pass the material and whether the material can be pulled smoothly, which involves a key point in film rolling production – C O. F (i.e. friction coefficient).
Friction coefficient, we often only consider two aspects during production:
One is the friction between the rolled film fabrics, and the other is the friction between the inner layers of the rolled film. When we conducted tests, we only focused on these two friction coefficients. But if it is the production of roll film, it is also necessary to consider the friction surface of the automatic packaging machine during the actual use of the customer. At this time, the friction between the surface layer or inner layer of the rolled film and the equipment directly determines its smoothness of feeding.
At the same time, we also need to pay attention to the friction data, which is the friction coefficient between the inner and outer layers. The magnitude of this coefficient will directly determine the smoothness of unwinding after the finished film is rolled. If the friction coefficient value is too high, the unwinding of this film will not be smooth when used by customers. This is the most basic control key point for the feeding of film on automated packaging equipment.
So we will need to better control the C.O.F for the PE roll stock.
Raw material quality means the quality of each PE film layer. The PE film needs to be in good quality, then it is possible to make good quality laminated mono-material PE roll stock.
If the friction coefficient of the raw material itself is very high, it is essentially impossible to reduce the friction coefficient in this state during subsequent production. But we can increase the smoothness of the rolled film by spraying powder. Powder coating is a method of increasing smoothness on the surface, that is, reducing the coefficient of friction.
However, when using such methods, it is important to consider what kind of powder to use, what the contents of the customer’s packaging are, whether there is any conflict or even chemical reaction with the powder. On the other hand, how to control the amount of powder spraying? If you spray too little, the effect will not be achieved, and if you spray too much, it will affect the sealing performance. Therefore, it is necessary to grasp this degree well.
What if the customer needs a product that is not so slippery, that is, one with a high coefficient of friction? This is probably not easy to do either. Experienced production personnel will also come up with a solution to increase the curing time to control (which is also one of the factors affecting the friction coefficient). This operation seems to be easier to master than powder coating. In fact, this is even more difficult to grasp: this is because powder spraying is a visible amount, and curing time is only a concept of time, but there is no actual measurement. Only by testing during a certain period of time can we know. In such a process, it is difficult to determine whether the entire roll can achieve the effect of improving the friction coefficient. So increasing the maturation time is much more difficult than spraying powder to reduce the friction coefficient. Therefore, maturation is actually a key point that affects the variation of friction coefficient.
So we can adjust the aging time to control the roll stock quality.
At present, polyurethane adhesives on the market generally do not have a significant impact on PE materials. However, there are some special adhesives, such as polyurethane adhesives containing certain ether components, which will react chemically and physically with PE based lubricants to a certain extent. Most of them will result in a lower smoothness of the inner film, that is, the friction coefficient of the originally smooth film will significantly increase after being compounded with ether based polyurethane adhesives.
So it will be better for us to always choose polyurethane adhesives.
The PE roll stock direction needs to be divided into the vertical direction, which is the mechanical direction. For some current devices, this direction is not a big problem, but as we all know, customers usually do not frequently change the conventional settings, such as the coding position, coding direction, and the folding direction of the middle seal bag (usually defined as the non barcode side, mainly considering the convenience of displaying product barcodes). Therefore, once the vertical direction is reversed, it is generally difficult for customers to accept.
On the other hand, the direction of the surface layer and the inner layer should not be reversed normally, but there are also some products that we can easily ignore and cause reversal, such as blank film. Sometimes, in order to control the winding tension well in the previous process, the heat sealing layer is placed on the outside, and if not noticed during cutting, it is easy to cause vertical reversal problems.
Generally, there are two main aspects:
The first issue is the flatness of the end face of the rolled film. In this regard, the standard requirement in the national standard is ± 2mm. However, for those narrow rolls of film, such as those with a roll width less than 50mm, if there is a 2mm deviation in flatness, the correction requirements for general automation equipment will be relatively high. However, the most fatal thing is that some automatic packaging equipment does not have a correction device at all, and the requirement for the flatness accuracy of the roll film end face will be higher. Otherwise, there will be deviations beyond the range during the automatic packaging process of the product.
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). Generally, products do not have high requirements for this aspect, but this curling degree will directly affect the packaging effect or efficiency of automatic packaging equipment. Some automatic packaging equipment even has very strict requirements for the curling of this rolled film, and if the curling degree of the rolled film exceeds 30 °, it is considered as a non-conforming product. The main processes that are affected by the curvature of the film roll include composite processes (including control of curing conditions) and control of the tension of the slitting process itself. In terms of composite, there will mainly be matching of winding and oven tension. If the optimal state is not reached, it may have a certain impact on general materials, and it is very easy to cause film warping problems.
So we will need to make sure the flatness is good for the roll stock.
Longdapac is one of the leading manufacturers in 100% recyclable mono-material PE laminated roll stock film products. After couple years R&D from Longdapac engineers, now we can supply same good quality as conventional material. This is getting good reputation in our customers.