First, the basic process of aluminum foil lamination 
Aluminum foil composite is a difficult structure of the solvent-free composite process, according to years of research and experimentation by industry professionals, aluminum foil composite can be mass produced, aluminum foil composite many users find it difficult to master, the main root causes of the problem in the following aspects: aluminum foil is a rigid substrate, thickness is very small, and the initial adhesive strength of the adhesive is relatively low, it is difficult to form a good initial lamination.

Aluminum foil lamination is usually a three-layer or four-layer structure. We recommend two methods: step-by-step method and one-step method.

1. Step-by-step method. The so-called step-by-step method is to laminate two layers at a time, three-layer structure in two times, and four-layer structure in three times.

Between the two laminations, either full or partial curing can be used.

We strongly recommend the partial cure method, which means that the next lamination is carried out within 2-4 hours of curing after lamination.

Partial curing method is original to Tomze, which can reduce backside failure, shorten production cycle and improve efficiency.

2. One-step method. The so-called one-step method of three- or four-layer lamination is completed in one go. It requires three-in-one equipment YWF1300S TRI model low station solventless laminator for operation.

The process is different, the problem situation is different.

Second, a few common difficulties in response to the operation

I) Composite white spots
This situation is more common in PET (printing film)/aluminum foil lamination.

Relatively speaking, aluminum foil glue is more viscous than other flexible packaging glue, it is more likely to be uneven distribution of multi-color ink thickness, resulting in the maturation process, the glue is difficult to completely fill the ink pits, the appearance of white spots (see Figure 1).

The main response methods:

(1) Selection of appropriate ink; selection of ink with finer particles can appropriately reduce the amount of glue.

(2) Appropriately reduce the machine speed; machine speed control at 100-150m/min.

3) Reasonably set the temperature of each steel roller. Metering roller temperature 40-45 ℃, coating steel roller 50-55 ℃, composite steel roller temperature 45-55 ℃. Of course, these should be selected according to the glue characteristics. 
II) Glue penetration back-stick (back-penetration)
This situation is more common in ordinary aluminum foil lamination.

The basic reason for this phenomenon is: the aluminum foil itself has a certain number of pinholes, and glue curing is a relatively slow process, the glue in the curing process under the action of the pressure in the volume through the aluminum foil pinhole infiltration, resulting in anti-adhesion, commonly known as back-through.

The main response method:

(1) Select aluminum foil with fewer pinholes. The thickness of the aluminum foil and the aluminum foil pinhole is directly related to the general thicker aluminum foil pinhole will be less, the less pinhole composite difficulty will be reduced. It is recommended to choose AL with grade A or above and 6.5μm-7μm.

2) Choose high viscosity glue, such as polyurethane vapor grade glue, AL special high viscosity glue. Because the aluminum foil composite speed is generally in the 100-150m/min majority, and because of the relatively low composite speed, it is necessary to choose a higher viscosity of the glue. Higher viscosity glue, molecular weight is relatively large, relatively smooth leveling, so it is more difficult to penetrate into the pinhole of aluminum foil, thus greatly reducing the phenomenon of glue anti-sticking.

(3) PET/aluminum foil lamination and then laminating the inner layer of the intermediate time reasonable control. The intermediate time is generally controlled in 2-4 hours. 
III) winding slippery roll

This kind of failure is more likely to occur in aluminum foil / PE composite.
The main reason for this situation is that the adhesive initial adhesion is low, when the amount of glue increases, the friction between the substrate will be reduced, coupled with a certain amount of air between the composite layer, in the large pressure or large tension will be prone to relative slippage.

The main response method:

(1) Reasonable control of the amount of gluing, and reduce the amount of gluing appropriately when the equipment is slowing down. The amount of glue is the most sensitive factor that leads to solvent-free laminating in the winding slippery roll. The characteristics of each material itself determines its own friction, so each material composite, we first need to find the glue volume caused by the winding slippery critical point. For example: Aluminum foil/PE gluing amount is generally controlled at 1.3-1.5 g/m², adjusted according to the thickness of PE film, the thicker the PE film, the larger the gluing amount, and the gluing amount is controlled at 1.1-1.2 g/m² when the speed is reduced. There is PET/AL/PE structure, generally solvent-free composite PE layer, resulting in the structure of the critical point of the gluing volume of the sliding volume is generally in the vicinity of 1.3 g/m², then we set the gluing volume at 1.1 g/m²-1.2 g/m² can be.

(2) Adjust the pressure of the winding pressure roller and roller cutting surface. Solvent-free lamination, the control of the winding pressure roller is also very critical. Winding pressure roller can change the tightness of the winding material to ensure that the winding is not slippery, winding pressure roller needs to do the following two points to ensure:

-Winding pressure roller and winding material balance.
-Air pressure of about 0.05MPa.

In addition to adjust the pressure roller through the pressure roller adjusting screws and paper tube cutting surface parallel to the pressure roller.

(3) Properly control the winding tension. The higher the winding tension, the tighter the material will be when winding, and the easier it is to slip the roll.

Example: PE / PE structure, the initial winding tension is set at 13kg, the amount of glue 1.3g / m², winding slippery rolls, the amount of glue changed to 1.1 g / m², or from time to time slippery rolls. Then reduce the amount of glue can not guarantee the peeling strength, then the winding tension to ensure that there is no core wrinkle case as small as possible.