What special processes are used when laminating kraft silicone paper onto the base paper to ensure a perfect and non-detachable bond between the film and the base paper?
Publish Time: 2026-02-02
Kraft silicone paper, as a high-performance composite material, is widely used in label backing paper, die-cutting release liner, food packaging, and industrial tapes. Its core structure typically uses high-strength kraft paper as the substrate, coated or laminated with an organic silicone coating to provide excellent release properties, temperature resistance, and chemical stability. However, in some high-end applications, to enhance mechanical strength, moisture resistance, or printability, a functional film is first laminated onto the kraft paper substrate before silicone coating. This "base paper lamination + silicone coating" composite process places extremely high demands on the bonding quality between the film and the base paper—it must ensure no bubbles, no wrinkles, no delamination, and maintain a strong bond even during subsequent high-temperature baking, high-speed die-cutting, or long-term storage. Therefore, the industry generally employs the following key special processes to achieve perfect bonding and durable adhesion.
1. Base Paper Surface Pretreatment: Enhancing Interfacial Activity and Wettability
While kraft paper possesses high strength and toughness, its rough fiber surface and presence of natural waxes and impurities can easily lead to insufficient adhesion when directly laminated. Therefore, rigorous surface pretreatment is essential before lamination. Common methods include corona treatment, plasma treatment, or flame treatment. Corona treatment is the most prevalent: high-frequency, high-voltage discharge generates free radicals and polar groups on the paper surface, significantly increasing surface energy. This makes the plastic film easier to wet and penetrate the paper's micropores during hot pressing, creating an "anchoring effect." This step is fundamental to ensuring initial tack and long-term bonding strength.
2. Selection and Precise Coating of Dedicated Environmentally Friendly Adhesives
Unlike ordinary laminated paper, which can use hot melt adhesives or water-based adhesives, kraft silicone paper requires subsequent high-temperature silicone curing at 150–200℃, necessitating extremely high requirements for the adhesive's heat resistance, flexibility, and chemical inertness. The industry primarily uses two-component polyurethane adhesives or modified acrylic adhesives, which are not only heat-resistant and non-yellowing, but also form a cross-linked network structure at the paper-film interface, resisting thermal expansion and contraction stress.
3. Coordinated Control of Temperature, Pressure, and Speed in Hot-Pressure Lamination
The hot-pressing parameters during lamination directly affect the lamination strength. For the combination of kraft paper and film, the hot roller temperature needs to be set at 80–110℃, the linear pressure controlled at 8–15 kg/cm, and a suitable machine speed matched. Excessive temperature will cause the paper to lose moisture and become brittle, while too low a temperature will result in unactivated adhesive; insufficient pressure leads to poor bonding, while excessive pressure will crush the paper fibers. Advanced equipment is equipped with infrared temperature measurement and a closed-loop feedback system to adjust parameters in real time, ensuring that the lamination interface completes molecular diffusion and physical integration within the optimal "window period."
4. Curing Process: Completing Final Cross-linking and Stress Release
Although the newly laminated semi-finished product has a smooth appearance, the adhesive layer is not yet fully cross-linked, and internal stress has not been released. Directly entering the silicone coating process can easily lead to curling or delamination during drying. Therefore, a constant-temperature curing process of 48–72 hours is necessary. During this process, the adhesive molecules fully cross-link, stable chemical bonds and van der Waals forces form at the paper-film interface, and the deformation of the paper caused by heat and pressure is restored, significantly improving overall dimensional stability. The cured composite base paper can withstand subsequent silicone curing at 200℃ for 30 seconds without delamination.
In summary, Kraft silicone paper achieves perfect fusion of the film and base paper at both the micro and macro levels through a unique five-in-one process system of "surface activation—special adhesive—precise hot pressing—full curing—intelligent quality control" in the base paper lamination stage. This not only ensures the release stability and processing adaptability of the end product but also supports its reliable application in demanding fields such as high-end electronics and new energy battery tapes, demonstrating the precision and systematic nature of material composite technology.
