Solvent-free lamination has matured in the market, mainly due to the efforts of packaging enterprises and material suppliers, especially pure aluminum lamination technology for retorting has been widely popularized, and has taken a big step under the environment conditions of replacing the traditional solvent-base lamination and extruded lamination production. Packaging enterprises are beset by various quality problems due to the different conditions of the products in equipment, operation, raw materials, quality technology and use. This paper will talk about an existing problem, namely, the ability of the pouch to open and its smoothness.
For example, a regular three-layer extruded polyethylene film is made up of corona layer, middle functional layer and bottom thermal seal layer. Normally, opening and smooth additives are added to the hot sealing layer. Smooth additive is transferred between 3 layers, and opening additivity is not.
As a hot-sealing material, opening and smooth additives are necessary when producing flexible packaging composites. They are essentially different, but most packaging manufacturers misunderstand that they are the same.
The general opening additive is commercially available silicon dioxide, which is an inorganic substance that can increase the film' s resistance to viscosity. Some customers always find that the two layers of the pouch seem to be hazy between them, just like two glasses that overlap. You'll notice that it' s smooth to open and wipe, which is typically lacking in opening additives. And even some film makers don't use it.
The general smooth additive is Erucic acid amide, which is the white powder that often adhere to the lamination roller and guide roller in the solvent-base laminating process. If an excess of smooth agent is added during the solvent-free laminating process, some will disperse to corona layer as curing temperature increases, resulting in decreased peeling strength. The original lamination transparent PE film peeled with white, can be wiped off with tissue. There is a way to analyze and test whether the reduced peeling strength is affected by an excess of smooth additives, placing the low strength laminate film in an oven at 80℃for five minutes, and then testing the strength. If it increases significantly, it is essentially concluded that the reduction in peeling strength is due to too much smooth agent.
Compared with rewind of solvent-base lamination, the solvent-free lamination method is much easier to achieve additive transfer and dispersion. The usual way to judge solvent free laminating rewind is to check that they are compact and neat enough to allow a better secondary smooth flow of solvent-free adhesives. The higher pressure the film roller fits, the more slippery additive is likely to migrate to the laminated layer, or even the printing layer. Therefore, we remain confused about this issue. What we can do is reduce the curing temperature, lower the coating weight, loosen the film, and add smooth additives again and again. But without a good control of above, the adhesive is difficult to cure and holds water. Too many additives will not only affect the peeling strength of the plastic pouch, but also affect its hot-sealing performance.
KANDA NEW MATERIALS has issued a series of adhesives to solve these problems. The WD8117A / B double component solvent-free adhesive is a good recommendation. It' s been authenticated by clients for a long time.
|
Structure |
Original coefficient of friction |
Laminated coefficient of friction |
|
PET/PE30 |
0.1~0.15 |
0.12~0.16 |
WD8117A / B can be used to solve the problem of poor peeling strength and thermal sealing performance due to excessive smooth additives of the surface without requiring the original film manufacturer to reduce them.
Additionally, WD8117A/B has two more properties:
1. The peeling strength of OPP / AL / PE is above 3.5 N, close to or higher than that of some solvent-base laminating adhesives.
2. Fast curing. Under the suggested conditions, laminating film can shorten curing period of about 8 hours, which hugely raise the production efficiency.
To sum up, the final determination of friction coefficient of composite film should be based on the static friction coefficients between film and steel plate. Misconceptions that it is difficult to open a pouch because there are not enough smoothing additives should be recognized and corrected. We can only achieve stability and superior flexible packaging products through each summary and update.
Post time: Jun-03-2019