The composite adhesives used in the domestic flexible packaging industry mainly include two-component polyurethane adhesives, water-soluble acrylic adhesives, water-soluble polyurethane adhesives, alcohol-soluble adhesives, and solvent-free adhesives.
1. Development and application of composite adhesives with high solid content, low viscosity and low solvent residue
Adhesives with high solid content and low viscosity have become an important development direction of dry composite adhesives. Under the same coating amount, the use of high solid content adhesive can effectively reduce the amount of solvent used, and has the following advantages: reduce solvent consumption; reduce drying load, improve production efficiency, reduce energy consumption; reduce solvent residues. Previously, the main solid content of two-component polyurethane adhesives was 35% or 50%, two-component polyurethane adhesives with a solid content of 75% accounted for 60% of the market share, and two-component polyurethane adhesives with a solid content of 50% accounted for 60% of the market share. The market share of pharmaceuticals is shrinking and is now less than 30%.
2. Development and application of water-based adhesives
The advantage of the water-based adhesive is that water replaces the organic solvent, there is no potential danger of combustion and explosion, it does not pollute the environment, it is non-toxic to operators, and the cost is low. However, this adhesive has poor coating properties and poor wettability to composite substrates, resulting in poor adhesion. Ordinary water-based adhesives are only suitable for some lightweight packaging. For some material structures with higher requirements, the performance of water-based adhesives needs to be further improved.
In 2007, water-based adhesives have been widely used, which is not only due to the recognition of consumers, but also to the cultivation of the water-based adhesive market by manufacturers, and also due to the continuous price of two-component polyurethane adhesive raw materials. The rising cost of solvent-based adhesives.
3. Develop solvent-free adhesives
Solvent-free adhesives are basically also composed of two-component polyurethane adhesives. The main agent and curing agent have high viscosity at room temperature, but they are still fluid and are semi-solid substances. The solvent-free composite process does not have the problem of organic waste gas emission, the equipment is simple, the energy consumption is low, it is suitable for reducing costs, saving resources and protecting the environment, so it will be the main development direction of the composite process in the future. Solvent-free adhesives can be used in most low-end and middle-grade composite flexible packaging, but due to the limitation of compound quality and other factors, solvent-free compounding cannot completely replace dry compounding. From a long-term perspective, with the increasingly stringent environmental regulations and the continuous development of the economy, the proportion of solvent-free adhesive products will continue to rise.
4. Development and application of alcohol-soluble polyurethane adhesives.
Alcohol-soluble polyurethane adhesives can use ethanol as a diluent. Under normal circumstances, there are less solvent residues. At the same time, the price of ethanol is cheap, which can effectively reduce the cost of compounding. In addition, the alcohol-soluble polyurethane adhesive has good compatibility and bonding performance with alcohol-soluble ink, and at the same time it can be cured at room temperature, saving the curing cost.

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