Introduction to the process performance of polyamide coatings, perchloroethylene coatings and organic fluorine coatings

China Coatings Online News Information: With the expansion of the scope of food safety definition, countries on food, agricultural products packaging requirements continue to improve. In the international market, many food and agricultural products are used in steel barrel packaging, its inner wall paint hygiene requirements have caused widespread concern, in order to meet the needs of the international market, China also export food and agricultural products packaging barrels of inner wall paint hygiene requirements made specific provisions. According to the regulations, food grade coatings allowed on the inner walls of the packaging barrels are polyamide coatings, perchloroethylene coatings and organic fluorine coatings.
epoxy coating belongs to epoxy resin coating, and epoxy resin coating belongs to cured film coating. Epoxy resins are generally made up of bisphenol A (biphenol-based propane) and epoxy chloropropane. Depending on the degree of polymerization, the molecular weight of epoxy resin is also different, from a health point of view, the larger the molecular weight (i.e. the smaller the epoxy value) the more stable, the less likely it is for harmful substances to dissolve into food, so the higher its safety. Polyamide, as a curing agent of polyamide epoxy resin coating, is itself a polymer compound, which has not been reported to be toxic. The quality of polyamide epoxy resin (epoxy value of epoxy resin) is closely related to the ratio and curing degree of curing agent. Curing agent ratio is appropriate, the higher the curing degree, epoxy resin coating to the food migration of less un cured substances. According to GB9686-88 "Food container wall polyamide epoxy resin coating hygiene standards", polyamide epoxy resin coating in a variety of solvents evaporation residue should be controlled at less than 30 mg / liter.
vinyl chloride coatings are made from perchloroethylene resin. With plasticizer, after painting and spraying the inner wall of the packaging barrel naturally dried into a film. Perchloroethylene coatings are generally divided into primers and finishes. Perchloroethylene resin contains perchloroethylene monosome, a cancer-causing toxic compound. The perchloroethylene coating after filming may still contain the residue of vinyl chloride, in accordance with GB7105-86 "food container perchloroethylene inner wall coating hygiene standards" after filming of the perchloroethylene coating vinyl chloride monosome residue should be controlled at less than 1 mg / kg. Additives such as plasticizers and solvents used in vinyl chloride coatings must comply with the relevant provisions of GB9685-94 "Health Standards for the Use of Additives for Food Containers and Packaging Barrel Materials" and must not use toxic or highly toxic additives. The coating is uniform and free of bubbles, spots, wrinkles and shedding.
Organic fluorine coatings include polyfluoroethylene, Teflon and Teflon coatings, which are aggregated from fluoroethylene, tetfluoroethylene and hexafluoropropylene as the main raw materials and are sprayed on the inner wall surface of the barrel with a certain additive. Organic fluorine coating has the characteristics of anti-adhesive corrosion resistance, but its acid resistance is poor, so it is widely used in honey-filled inner coating barrels on the steel drum. In terms of application, the organic fluorine coating on the inner honey packaging barrel is Teflon, referred to as PVF coating. It is a polymer compound, chemical properties are stable, generally there will be no monosome residue, is a relatively safe food packaging barrel wall coating. However, when cleaning the inner wall of the drum steel barrel, most of the current packaging barrel production enterprises are using spray cleaning trunks for cleaning. The cleaning agent is commonly used chromate, which may cause chromium salt to remain on the surface of the container, which in turn can be mixed into the inner wall coating.
refore, in the production of inner wall honey packaging barrel steel barrels, should be in accordance with GB1167-89 "food container inner wall Teteflon coating hygiene standards" for inner wall honey packaging barrels steel barrels for inspection. The standard stipulates that the appropriate amount of chromium and fluorine should be controlled between 0.01 mg/L and 0.2 mg/L, respectively. In addition, Teflon in the baking, if the temperature reaches 280 degrees C will occur fission, the production of highly volatile toxic fluoride, so, in the use of Teflon inner wall honey packaging barrels, the general baking temperature should not exceed 250 degrees C.