Coating knowledge: introduction to process performance of polyamide coating, perchloroethylene coating and organic fluorine coating

Core tip: as the scope of food safety definition continues to expand, countries' requirements for food and agricultural product packaging continue to improve In the international market, many food and agricultural products are packaged in steel drums, and the hygienic requirements of the inner wall coating have attracted wide attention of all countries In order to meet the needs of the international market, China has also made specific regulations on the hygienic requirements of the inner wall coating of packaging barrels for export food and agricultural products According to the regulations, the food grade coatings allowed to be used on the inner wall of the packaging barrel include polyamide coating, perchloroethylene coating, organic fluorine coating, etc Polyamide epoxy coating belongs to epoxy coating, and epoxy coating belongs to curing film coating Which is the price of Dajin diatom mud Recommended brief introduction: which is the price of Dajin diatom mud? 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Guangdong diatom mud agent suggests placing a basin of cold water in the air conditioning room, so that the diatom mud wall can breathe effectively The feature of the breathing wall is obvious When the indoor air is dry, the diatom mud wall will release the absorbed water quickly Put it out to help regulate the indoor dry humidity It is suggested to place a basin of cold water in the air conditioning room, so that the wall of diatom mud can breathe effectively The feature of the wall that can breathe is obvious When the indoor air is relatively dry, the wall of diatom mud will absorb the water Home of coatings news: with the expansion of the definition of food safety, the packaging requirements of food and agricultural products in various countries continue to improve In the international market, many food and agricultural products are packaged in steel drums, and the hygienic requirements of the inner wall coating have attracted wide attention of all countries In order to meet the needs of the international market, China has also made specific regulations on the hygienic requirements of the inner wall coating of packaging barrels for export food and agricultural products According to the regulations, the food grade coatings allowed to be used on the inner wall of the packaging barrel include polyamide coating, perchloroethylene coating, organic fluorine coating, etc Polyamide epoxy coating belongs to epoxy coating, and epoxy coating belongs to curing film coating Epoxy resin is generally made by polymerization of bisphenol A (diphenylpropane) and epichlorohydrin According to the degree of polymerization, the molecular weight of epoxy resin is also different From the perspective of health, the larger the molecular weight (i.e the smaller the epoxy value), the more stable it is, the less likely it is for harmful substances to dissolve and migrate into food, so the higher its safety Polyamide, as the curing agent of polyamide epoxy resin coating, is a kind of high polymer compound, and no toxic report has been found The quality (epoxy value) of polyamide epoxy resin is closely related to the ratio of curing agent and curing degree If the ratio of curing agent is appropriate, the higher the curing degree is, the less the uncured substance will migrate to food According to gb9686-88 hygienic standard for polyamide epoxy coating on the inner wall of food containers, the evaporation residue of polyamide epoxy coating in various solvents should be controlled below 30mg / L Perchloroethylene resin is used as raw material for perchloroethylene coating With plasticizer, the inner wall of the packaging barrel is painted and sprayed to form a film naturally Perchloroethylene coating is generally divided into primer and finish Perchloroethylene resin contains perchloroethylene monomer, which is a carcinogenic toxic compound The perchloroethylene coating after film forming may still contain the residual of vinyl chloride The residual of vinyl chloride monomer in the perchloroethylene coating after film forming shall be controlled below 1 mg / kg according to gb7105-86 hygienic standard for perchloroethylene inner wall coating of food containers Plasticizers, solvents and other additives used in perchloroethylene paint must comply with the relevant provisions of gb9685-94 hygienic standard for the use of additives for food containers and packaging barrels, and toxic or highly toxic additives shall not be used The coating shall be uniform without bubbles, spots, wrinkles and falling off Organic fluorine coatings include polyfluoroethylene, polytetrafluoroethylene and polyhexafluoropropylene coatings These coatings are polymerized with fluorine ethylene, tetrafluoroethylene and hexafluoropropylene as main raw materials, and are sprayed on the inner wall surface of the packaging barrel with certain additives Organic fluorine coating has the characteristics of anti adhesion and anti-corrosion, but its acid resistance is poor, so it is widely used in the steel barrel containing honey inner coating packaging barrel In terms of application, the organic fluorine coating on the inner honey packing barrel is polytetrafluoroethylene, which is called PVF coating for short It is a kind of high molecular compound with stable chemical properties, and generally there is no monomer residue It is a relatively safe coating for the inner wall of food packaging barrel However, when cleaning the inner wall of the steel drum, most of the current packaging drum manufacturers use spray cleaning and drying line for cleaning The cleaning agent is usually chromate, which may cause the chromate to remain on the surface of the container and then mix into the inner wall coating Therefore, in the production of inner wall honey packaging barrels, the inner wall honey packaging barrels should be inspected according to gb1167-89 hygienic standard for polytetrafluoroethylene coating on the inner wall of food containers The standard stipulates that the appropriate amount of chromium and fluorine shall be controlled between 0.01 mg / L and 0.2 mg / L respectively In addition, when polytetrafluoroethylene is baked, if the temperature reaches 280 ℃, it will fission and produce toxic fluoride with strong volatility Therefore, when using the honey packaging barrel with inner wall of polytetrafluoroethylene, the baking temperature shall not exceed 250 ℃ [focus on WeChat official account "paint net"; pay attention to surprises; scan code to see what the paint sales are Great! 》Paint home is specialized in coating, diatom mud, paint coating, coating process, news information and coating of fireproof coating, diatom mud, paint coating, coating process, decoration knowledge and decoration effect map of fireproof coating,