Requirements for Metal Packaging Inner Wall Coating (Export Food)

With the expansion of the scope of the definition of food safety, the Packaging requirements for food and agricultural products in various countries are constantly increasing. In the international market, many food and agricultural products are packed in steel drums, and the sanitary requirements of the interior wall coatings have attracted widespread attention from countries. As early as the 50s of the last century, the FDA in the United States demanded that food and agricultural product packaging barrels be highly regarded. In order to meet the needs of the international market, China has also made specific provisions on the sanitary requirements for the export of food and agricultural product packaging barrels.

At present, China's interior coated steel drums for food and agricultural products generally include honey buckets, juice buckets, and ketchup buckets. If the inner coating drum used for containing these foods, the hygienic quality of the inner wall paint fails to meet the safety food hygiene requirements, it will cause secondary pollution to the food, thereby affecting the intrinsic quality of the product.

According to the regulations, food-grade coatings that are allowed to be used on the inner wall of drums of packaging drums include: polyamide epoxy coatings, peroxyethylene coatings, and organic fluorine coatings.

Polyamide epoxy resin coatings are epoxy resin coatings, while epoxy resin coatings are cured film coatings. Epoxy resins are generally made from the polymerization of bisphenol A (bisphenol propane) and epichlorohydrin. According to the degree of polymerization, the molecular weight of the epoxy resin is also different. From the hygienic point of view, the larger the molecular weight (ie, the smaller the epoxy value) is, the more stable it is, and the less likely it is that the harmful substances will migrate into the food, so the safety is higher. As a curing agent for a polyamide epoxy resin coating, polyamide itself is a high molecular compound, and no report of its toxicity has been found. The quality of the polyamide epoxy resin (the epoxy value of the epoxy resin) is closely related to the ratio of the curing agent and the degree of cure. The proper proportion of curing agent and the higher the degree of curing, the less uncured material in the epoxy resin coating migrates into the food. According to the provisions of GB9686-88 “Sanitary Standard for Polyamide Epoxy Resin Coatings on Inner Walls of Food Containers”, the evaporation residue of polyamide epoxy coating in various solvents should be controlled below 30 mg/L.

Perchloroethylene paint uses vinyl chloride resin as raw material, together with plasticizer, and is naturally dried and filmed after being painted or sprayed on the inner wall of the packaging drum. Perchloroethylene coatings are generally divided into primers and topcoats. Perchloroethylene resin contains vinyl chloride monomer, which is a carcinogenic and toxic compound. The vinyl chloride coating after film formation may still contain residual vinyl chloride. According to GB7105-86 "Hygienic Standards for Perchloroethylene Inner Wall Coating of Food Containers", the residual vinyl chloride monomer in the vinyl chloride coating after film formation should be controlled. 1 mg/kg or less. Plasticizers, solvents, and other additives used in perchloroethylene coatings must comply with the relevant provisions of GB9685-94 "Hygienic Standards for the Use of Additives for Food Containers and Packaging Materials," and must not use toxic or highly toxic additives. The film is required to be uniform and free of bubbles, spots, wrinkles and shedding.

Organic fluorine coatings include polyvinyl fluoride, polytetrafluoroethylene and polyhexafluoropropylene coatings. These coatings are polymerized with vinyl fluoride, tetrafluoroethylene and hexafluoropropylene as the main raw materials, and are accompanied by certain additives. The inner wall surface. The organic fluorine coating has the characteristics of anti-sticking and corrosion resistance, but its acid resistance is poor, so it is widely used in inner coating drums containing honey. In terms of application, the organic fluorine coating on the inner barrel of honey coated barrel is PTFE, which is abbreviated as PVF coating. It is a kind of macromolecule compound with stable chemical properties. Under normal circumstances there will be no monomer residue. It is a relatively safe food packaging barrel wall coating. However, when cleaning the inner wall of the barrel of a packaging drum, most of the production enterprises of the packaging barrel currently use a spray cleaning and drying line for cleaning. Chromate is commonly used as a cleaning agent, which may cause chromium salts to remain on the surface of the container and then mix in the paint.

Therefore, in the production of steel drums coated with honey, should be in accordance with GB1167-89 "food container PTFE coating on the inner wall of the health standards," the inner coating of honey barrel drums for inspection. The standard states that the appropriate amount of chromium and fluorine should be controlled between 0.01 mg/l and 0.2 mg/l, respectively. In addition, when PTFE is baked, if the temperature reaches 280°C, fission will occur, resulting in highly volatile toxic fluorides. Therefore, when using PTFE coated honey drums, generally The baking temperature must not exceed 250 °C.

In recent years, China's exports of fruit juices, ketchup, and honey have often been returned overseas due to excessive pesticide levels. As a food packaging drum, the residual amount of solvent on the inner wall should be as low as possible. Therefore, in the production of food packaging bucket, must be in accordance with food safety and hygiene requirements, to ensure that the food packaging barrel cleaning and residual pest content does not exceed the health standards. To this end, a monitoring system should be formed in a chained manner. The use of food packaging barrels should require the packaging drum manufacturer to obtain a food safety and health inspection report for the packaging barrels; the packaging barrel production company should obtain the food safety of the interior coating from the coating supplier. Health inspection report. At the same time, relevant departments should also regularly supervise and inspect food packaging barrels and issue inspection reports.