From the packaging containers used in the current market for soft cans, they can be roughly classified into three types: a bag shape (commonly known as a retort bag), a disk shape (commonly known as a cooking container), and a cylindrical shape. These packaging materials are either single-layer plastic films or composite products of plastic film and aluminum foil. The composite film packaging material used for soft can, the outer film is nylon, polyester; the film as the barrier layer is polyvinylidene chloride, aluminum foil, ethylene-vinyl alcohol copolymer; the film as the sealing layer has polypropylene, special Polyethylene, etc. According to relevant experts in the industry, the various raw materials used in the composite film have the following characteristics:
Polyester: Polyester has excellent transparency, heat resistance and abrasion resistance. The film is available in 12 micron and 25 micron thicknesses and is printed on polyester. It can be used as a retort or disc-shaped lid.
Nylon: Nylon is indispensable as a substrate for soft can packaging materials, mainly biaxially stretched and unstretched. The biaxially stretched nylon 6 film not only has excellent heat resistance and cold resistance, but also has good tear strength and pinhole resistance, and can be used in combination with other raw materials. In addition, in order to prevent curling and increase strength, nylon 6-6 film is also used, but the price is higher than nylon 6.
Polyvinylidene chloride: Polyvinylidene chloride can also be used as a single-layer film in soft cans. It can be used as a packaging material for ham and sausage. It has excellent sealing, ligation, heat shrinkage and gas barrier properties. Polyvinylidene chloride can also be used as a coating for membranes such as nylon and polyester. In addition, it can also be used as a composite material for retort pouches for high-temperature, high-pressure sterilization of high barrier films.
High Density Polyethylene: Special high density polyethylene for soft cans is commercially available in Japan. Although the film has poor gas barrier properties, it can be used as a sealing layer because of its excellent tensile strength, elongation, tear strength, and good sealability. However, high-density polyethylene has poor heat resistance and its maximum heat-resistant temperature is 120 °C. Polypropylene: Polypropylene has good transparency and oil resistance, and its heat resistance is better than that of special polyethylene, so it can be used as a sealing layer for retort pouches and cooking containers. Most of the soft can packaging materials are unstretched polypropylene films or sheets as their sealing layer.
Aluminum foil: Aluminum foil is made of electrolytic aluminum with a purity of 90% or more. When used as a packaging material, aluminum foil is the only metal substrate in the packaging composite. The aluminum foil used for cooking is 7-15 microns thick, and the aluminum foil used in the cooking vessel is 50-130 microns thick. Aluminum foil is non-toxic, odorless, has excellent light-shielding properties, has high moisture resistance, gas barrier and confidentiality, and can most effectively protect the packaged material, and is most suitable as a packaging material for fat-containing foods. However, since there is a risk of pinholes occurring after the aluminum foil is bent, it is necessary to use a plastic film as an outer layer to be composited therewith.
Most of the packaging materials for soft cans are made of plastic film and aluminum foil. However, due to the type of packaged food, sterilization temperature and storage conditions, the combination of various raw materials must be carefully considered in use.