As for the classification and application range of CPP of high-temperature cooking bag materials, most of them use CPP materials. Due to the different material categories of CPP, its temperature resistance is also different. Here, I would like to introduce the classification and application range of commonly used CPP.
(1) general type.The multilayer coextruded film has different coextruded layers for different purposes.For example, bread packaging, clothes packaging (especially underwear and trousers), fruit packaging, etc. used in automatic packaging machine, or two layers of BOPP/CPP after printing, used for clothing, dry food (such as instant noodle bag, bowl cover, etc.) packaging.The general structure is copolymerization PP/ homopolymer PP/ copolymer PP or homopolymerization.
(2) metallization type.The surface of the product is required to have a strong adhesion strength to the epc (such as aluminum), which can maintain good dimensional stability and rigidity after evaporation.In addition, it has lower heat seal temperature and higher heat seal strength.The metallized structure is also copolymerized PP/ homopolymer PP/ copolymer PP.
(3) cooking type.Used for cooking the second copolymerization of CPP, able to withstand 120 ℃ and 0.15 MPa pressure cooking sterilization.It not only maintains the shape and flavor of internal food, but also does not crack, peel or stick the film, and has excellent dimensional stability. It is often compound with nylon film or polyester film, and the packaging contains soup food, meat balls, dumplings and other food or pre-processed frozen food.The boiling type three-layer PP film structure is copolymerized PP/ copolymer PP/ copolymer PP.
(4) high temperature cooking type.Packaging roast chicken, barbecued spareribs and jam, beverage, 121 ~ 121 ℃ high temperature sterilization of the three layers of copolymerization CPP film, including copolymerization PP requirements than the general type cooking copolymerization PP have better performance.
In addition to the three-layer film, there are five layers of fluid delay barrier packaging, whose structure is PP/ adhesive /PA/ adhesive/copolymerization PE.PP/ adhesive /PA/ adhesive /EVA;PP/ binder /EVOH/ binder /PE;PP/ adhesive /EVOH/ adhesive /EVA;PP/ adhesive /EVOH/ adhesive /PP, etc.
CPP films used for cooking packaging bags should be made from copolypropylene or blend modified polypropylene granules instead of polypropylene.Because the CPP film made of homogeneous polypropylene will be brittle after being boiled at high temperature, the seal is easy to break during the drop test, resulting in content leakage.
In addition, the limit temperature of the inner layer thin film adhesion, medium density polyethylene is 110 ℃, special polyethylene is 120 ℃, polypropylene is 125 ℃, special polypropylene is 140 ℃.
For custom retort packaging, see below：