Abstract:If you want to make solvent-free compound process using steadily, it is important to choose the composite adhesive correctly.This article introduces how to choose the most suitable solvent-free composite adhesive for composite substrates and structures.
With the maturity and popularization of solvent-free composite technology, more and more thin film substrates can be used for solvent-free composite. To use solvent-free composite technology stably, it is crucial to choose the correct composite adhesive. Below, based on the author’s experience, we will introduce how to choose a suitable solvent-free adhesive.
At present, dry lamination and solvent-free lamination coexist. Therefore, to stabilize the use of solvent-free lamination technology, the first point is to fully understand the product structure of the packaging factory, classify the product structure in detail, classify the product structures that can be used for solvent-free lamination, and then choose the appropriate solvent-free adhesive. So, how to effectively choose solvent-free adhesives? Match one by one from the following aspects.
- adhesive strength
Due to the complexity and diversity of packaging materials, the surface treatment of substrates also varies greatly. Common flexible packaging materials also have different characteristics, such as PE, BOPP, PET, PA, CPP, VMPET, VMCPP, etc. There are also some materials that are not commonly used in flexible packaging, such as PS, PVC, EVA, PT, PC, paper, etc. Therefore, the solvent-free adhesive chosen by enterprises should have good adhesion to most flexible packaging materials.
- Temperature resistance
Temperature resistance includes two aspects. One is high temperature resistance. Currently, many foods need to undergo high-temperature sterilization, some are sterilized at 80-100 ° C, while others are sterilized at 100-135 ° C. The sterilization time varies, with some requiring 10-20 minutes and others requiring 40 minutes. Some are still sterilized with ethylene oxide. Different materials have different sterilization methods. But the selected solvent-free adhesive must meet these high temperature requirements. The bag cannot delaminate or deform after high temperature. In addition, the material cured with solvent-free adhesive should be able to withstand high temperatures of 200 ° C or even 350 ° C instantly. If this cannot be achieved,bag heat sealing is prone to delamination.
The second is low temperature resistance, which is also known as freezing resistance. Many soft packaging materials contain frozen food, which requires solvent-free adhesives to be able to withstand low temperatures. At low temperatures, the materials solidified by the adhesives themselves are prone to hardening, brittleness, delamination, and fracture. If these phenomena occur, it indicates that the selected adhesives cannot withstand low temperatures.
Therefore, when choosing solvent-free adhesives, a detailed understanding and testing of temperature resistance are necessary.
3.Health and Safety
The solvent-free adhesives used in food and drug packaging should have good hygiene and safety performance. Strict regulations are in place in various countries around the world. The US FDA categorizes adhesives used in composite packaging materials for food and drugs as additives, limiting the raw materials used to manufacture adhesives and prohibiting the use of substances that are not included in the approved list of raw materials,And the composite materials manufactured with this adhesive are classified and limited in their application temperature range, including room temperature use, boiling disinfection use, 122 ° C steaming sterilization use, or 135 ° C and above high-temperature steaming sterilization use. At the same time, inspection items, testing methods, and technical indicators for packaging materials are also formulated. There are also relevant provisions and restrictions in China’s standard GB9685.Therefore, solvent-free adhesives used for foreign trade export products must comply with local regulations.
4.Meeting the needs of special applications
The widespread use of solvent-free composites in the field of flexible packaging has promoted their extension to related fields. Currently, there are special areas where they have been applied:
4.1 Solvent free composite PET sheet packaging
PET sheets are mainly made of PET materials with a thickness of 0.4mm or more. Due to the thickness and rigidity of this material, it is necessary to choose a solvent-free adhesive with high initial adhesion and viscosity to make this material.The finished product made of this type of composite material usually needs to be made into various shapes, some of which require stamping, so the requirements for peel strength are also relatively high. WD8966 produced by Kangda New Materials has high initial adhesion and stamping resistance, and has been successfully applied in PET sheet composite.
4.2 Solvent free composite non-woven fabric packaging
Non woven fabrics are widely used and have a variety of types. The application of non-woven fabrics in solvent-free environments mainly depends on the thickness of the non-woven fabric and the density of the fibers. Relatively speaking, the denser the non-woven fabric, the better the solvent-free composite. Currently, single component polyurethane hot melt adhesive is mostly used for solvent-free composite non-woven fabrics.
Post time: Dec-12-2023