When using two-component polyurethane adhesive composite paper and plastic, please be careful of these 4 points!
1. Two-component polyurethane adhesive is a reactive adhesive, and it is extremely sensitive to the content of water and alcohol in the solvent. At the same time, because the composite paper also has a certain amount of moisture, these will affect the full bonding of the polyurethane adhesive. Therefore, great care must be taken in compounding.
2. The surface of the paper is rough and has more pores. Compared with plastic-plastic composites, the amount of glue is large, otherwise it will affect the composite strength or produce air bubbles.
3. Moisture of composite paper. Too much humidity will also cause foaming of the composite membrane. The author encountered a case in Hunan, where a flexible packaging manufacturer produced paper-plastic packaging bags of betel nut products, the structure of which was OPP printing / paper / PE. The compounded product is impeccable in appearance and peel strength, but bubbles were found in the heat seal during the bag making process.
This phenomenon occurs in the middle of the hot scalpel, and there are no air bubbles in the heat-sealed sides. The bag making process of forming two packaging bags at a time is adopted. The hot iron on both sides is narrow, and the middle hot iron is wide. After heat sealing, it is cut into two bags by a blade.
The air bubbles are generated in the wide heat seal place in the middle, and no air bubbles appear on the heat seal places on both sides. Later, through adjustment, when making the bag, the composite film was cut open with a blade in the middle of the two packaging bags, and then the heat sealing was performed to eliminate the bubble phenomenon.
When cutting the composite film, because the moisture content of the paper is too high, the water vapor expands during heat sealing. The narrower heat seals on both sides can run out of the cut, and because there is no cut in the middle, the water can only blow bubbles inside. .
4. Since the polyurethane adhesive is a reactive two-component adhesive, the relative initial tack is poor when laminating paper. After the plastic film is glued during lamination, the temperature of the drying tunnel should not be too high, the tension should not be too high, and the temperature of the composite roller should not be too High, otherwise it is prone to curl or wrinkle.