Control Difficulties and Countermeasures in Aluminum Foil Lamination

Author: Guangzhou Tongze Machinery Co., Ltd.

A006 - Control Difficulties and Countermeasures in Aluminum Foil Lamination

Aluminum foil lamination is a difficult structure in the solventless lamination process, and many users find this structure rather hard to master. The root causes of the problems lie mainly in the following aspects: relatively high rigidity of aluminum foil, very small thickness of aluminum foil commonly used in flexible packaging, and relatively low initial tack of the adhesive.

The most common structures for aluminum foil lamination are PET/aluminum foil/PE, or BOPP/aluminum foil/PE. They can be completed by the two-step method (two layers laminated in two passes) or the one-step method (three layers laminated at once), and the situations in which problems occur differ.

Based on our years of experience working with users, the common problems with this structure still follow certain patterns.

I. Lamination white spots

This is relatively common in PET (printed film)/aluminum foil lamination.

Because aluminum foil adhesives generally have relatively high viscosity, the uneven thickness distribution of multi-color inks makes it difficult for the adhesive to fill the pits in the ink during curing, producing white spots (see Figure 1).

Main countermeasures:

1. Select suitable ink;
2. Appropriately reduce machine speed;
3. Set the temperature of each steel roller properly.

II. Adhesive penetration and reverse blocking (also called back-through)

This is relatively common in PET/aluminum foil lamination.

Because both sides of PET are corona-treated surfaces, the adhesive can penetrate through the pinholes of the aluminum foil, causing reverse blocking.

Main countermeasures:

1. Choose aluminum foil with fewer pinholes;
2. Properly control the interval time before laminating the inner layer after the PET/aluminum foil lamination is completed.

III. Winding slippage

This is relatively likely to occur during aluminum foil/PE lamination (see Figure 2).

Main countermeasures:

1. Properly control the adhesive coat weight, and appropriately reduce the coat weight when the equipment slows down;
2. Appropriately reduce the adhesive coat weight;
3. Adjust the pressure of the winding nip roller and the cut surface of the nip roller.

IV. Soft wrinkles in winding

This situation mostly occurs at the core and splice positions (see Figure 3).

Main countermeasures:

1. Use a better core or a printing plate cylinder as the core;
2. Properly control the winding tension and taper.

(Reprinted from WeChat official account: Tongze Solventless Lamination)