Flexible packaging, also known as soft cans, has surpassed hard packaging such as plastic, glass bottles and cans due to its unique comprehensive performance including being lightweight and convenient, having a long shelf life, being hygienic, easy to store and transport, easy to open, generating less waste and having a good shelf effect. Due to its excellent performance, polyurethane adhesives can bond film materials of different properties together to obtain composite films for flexible packaging with various properties such as cold resistance, oil resistance, chemical resistance, transparency and wear resistance.