In the commonly used metal bucket paints, there are mainly two types of fluorine paints and epoxy paints, but the most excellent paint adhesion to metal barrels is epoxy paints, and epoxy paints have outstanding anti-corrosion performance. Epoxy coating is the earliest, most common and most traditional internal coating in the domestic metal barrel industry.
Currently, there are five types of epoxy coatings widely used by domestic metal barrel manufacturers: colorless transparent (X-620), golden transparent (X-621), and beige enamel (X-622), which require baking and curing. Ambient temperature two-component solid colorless transparent (X-623) and white tile color (X-624).
Epoxy resin properties
One of the main film forming materials for epoxy coatings is epoxy resin.
Epoxy resin generally refers to a polymer that contains two or more epoxy groups and is based on aliphatic, alicyclic or aromatic skeletons. Due to the different raw materials and synthetic processes used, the properties and molecular weight of epoxy resins are different, and they have liquid, viscous, and solid forms.
In general, it can basically be divided into glycidyl ether type resin, glycidyl ester type resin, glycidyl amine type resin, alicyclic epoxy compound, linear alicyclic epoxy compound, modified epoxy resin (such as elemental silicone, phosphorus epoxy resin and polyurethane epoxy resin, etc.) and bisphenol A type resin.
The epoxy resin used in the X-62 series metal bucket coating is a bisphenol A diglycidyl ether (DGEBPA) resin formed by the polymerization of epichlorohydrin and bisphenol A in the presence of sodium hydroxide.
Since both epichlorohydrin and bisphenol A are difunctional compounds, such epoxy resins are linear structures. This epoxy resin contains hydroxyl groups, ether groups, and very reactive epoxy groups. Among them, hydroxyl and ether groups have strong polarity, which makes the epoxy resin produce stronger interaction with the adjacent interface. Therefore, the coating for X-62 series metal buckets has a strong adhesion to the surface of the metal bucket, and the active epoxy group gives a high-strength bonding force to the surface of the coating and the metal bucket.
The molecular chain of the bisphenol A diglycidyl ether (DGEBPA) type epoxy resin used in the X-62 series metal bucket coating is a carbon-carbon bond and an ether bond structure, and its chemical properties are very stable. Therefore, its chemical resistance, acid and alkali resistance are very good. In addition, since the epoxy group of this epoxy resin is at the two ends of the molecule, the internal rotation resistance of the molecular chain is small, and the epoxy resin used for the X-62 series metal bucket coating is softened with a low viscosity. , so it's more flexible. This is very suitable for the internal coating process of the metal barrel industry (the barrel body and the bottom and the top of the barrel are separately coated, baked and cured, and then re-rolled).
The X-62 series metal bucket coatings utilize the reactive epoxy groups in the epoxy resin structure to cross-link and cure with a variety of organic compounds to form a solid three-dimensional network structure with four different special organic materials and rings. The active epoxy groups in the oxygen resin structure are cross-linked to form coatings with different colors and different curing conditions, so that the mechanical properties and chemical resistance of the X-62 series coatings are further enhanced.
Characteristics of X-62 Series Metal Barrel Coatings
1. The bisphenol A diglycidyl ether (DGEBPA) type epoxy resin used in X-62 series metal bucket interior paints is treated with "X-6 technology" with low viscosity and softness, so under the same resin content conditions, Its low viscosity makes it easy to form a thick coating film at a time and is beneficial to a coating and baking process of a metal barrel.
2. The softener is not added to the X-62 series metal bucket inner coating. The softener is softened by increasing the molecular gap of the epoxy resin, but at the same time as achieving softness, the corrosion resistance of the coated film is affected due to the increase of the molecular gap of the epoxy resin. The epoxy resin used in the X-62 series metal bucket coating is soft and low-viscosity treatment, so even if no softener is added, it can be curled freely after being applied to a metal bucket.
3. Additives, leveling agents, defoamers and other additives are not added to the internal coatings of X-62 series metal drums. As these additives improve the coating performance of epoxy coatings, they also have a certain influence on the cross-linking of epoxy resins and different organic substances, which can easily cause the defects of the three-dimensional network structure membrane, so that the anti-corrosion performance of the coatings is eventually affected. influences.
4. The internal coating of X-62 series metal buckets is completely made of imported rutile titanium dioxide particles treated with particles as pigments and fillers, eliminating the use of cheap pigments and fillers such as talcum powder, calcium carbonate, barium sulfate, and zinc antimony white. Therefore, the coating surface is bright and smooth, and the coating film has excellent anti-corrosion properties.
5. Because the bisphenol A diglycidyl ether (DGEBPA) type epoxy resin used in X-62 series metal bucket inner paint contains polar hydroxyl and ether bonds, it can form chemical bonds with the metal surface free bond, so Metal buckets are the best coatings.
6. After the X-62 series metal bucket interior paint is cross-linked and cured, the coating film forms a three-dimensional three-dimensional structure, the structural stability of the carbon-carbon and ether bonds in the molecular chain is greatly enhanced, and the coating structure is further improved. Dense, so enhance the chemical resistance of the coating, making the coating further enhance the ability to resist the corrosion of the integrated medium
Comparison of performance of various types of X-62 metal bucket paint
1. X-620 coating is colorless, odorless, transparent, strong and tough, and resistant to boiling. The inside of the metal barrel coated with this kind of paint is sanitary and smooth, that is, using a clean white napkin to sweep the entire metal barrel is clean and new and spotless. Therefore, it is most suitable for food products such as fruit juices, beverages, and oils; the inner coating of the open metal bucket with this kind of paint has a special visual effect, as if it is coated with a thin layer of crystal clear crystal. The inner wall of the metal barrel is like a stainless steel mirror panel. Its anti-corrosion and anti-rust function is very strong, that is, in the presence of wet and chemically corrosive gases or liquids stored for several years will not rust; due to this type of paint also has UV resistance, light retention, color retention, some The barrel factory coated the paint on the inner and outer surfaces of the cold-rolled plate metal barrel at the same time, and even replaced the stainless steel metal barrel; some barrel factories processed it into various colors and used the outer coating of the metal barrel to make the metal barrel in the filling. Corrosive chemical liquids of all kinds can still be dazzling, without any influence of corrosion.
2. After the X-621 coating has been baked, it has a very bright golden transparent color. It looks like a gold glittering and beautiful appearance. The metal bucket coated with this kind of coating is most suitable for containing all kinds of sulfur-containing foods and acidic foods. Can hold most of the chemical liquids, in fact most of today's food cans are painted inside. The paint was sent to Europe by a Taiwanese-funded company in Shanghai and was in full compliance with European food packaging paint standards. Therefore, they have applied this paint to a large number of pure water packages for export to Europe.
3, X-622 paint was yellow after baking. It is currently the most widely used coating material in the metal barrel industry. After this coating is fully cured, it can be used for food packaging and has excellent anti-corrosion properties. The food hygiene index of this coating is several times better than the national standard, and it has passed the international SGS certification and meets the FDA standards for food and drug coatings. Therefore, metal buckets coated with this kind of paint can contain food items such as honey, tomato sauce and salted food, and can also contain a large number of wide-ranging chemical products.
4, X-623 and X-324 are actually the same product, but one is transparent and the other is white. Both of these coatings are two-component. When used, the two components are mixed together and cured at room temperature. However, even though room temperature conditions can be dry for more than ten minutes, it can be dry for about half an hour. It looks like it is completely cured, but it is only dry, not solidified. The complete curing at room temperature will take up to seven days (actually, the inventory of metal barrels in the barrel factory will be more than seven days); however, if it can be baked at low temperature for more than ten minutes, it can be completely cured. These two coatings have excellent water, solvent and chemical resistance after they are fully cured, making them suitable for the production of metal-coated barrels in barrel plants where there are no baking conditions and the production requirements are not high.
The properties of X-623 and X-624 coatings are similar to that of X-620 coatings. In particular, the visual effects of X-623 are almost the same as those of the X-620. Some barrel factories use their colorless, transparent, corrosion-resistant and room-temperature curing features. A thin layer of X-623 paint is applied to the top of the metal barrel coated with amino paint, so that when the metal barrel is filled with corrosive chemical liquid, it is not afraid to damage the paint surface. The interior of the X-624 paint was coated with a metal bucket. The inner wall was white as snow, smooth as porcelain, and bright as a mirror, as if it were lined with a single layer of white tiles.
The X-62 series paint was successfully developed by the Shanghai Chemical Cooperage Factory in 1962, so it was named as Type 62. It has been used for 45 years in metal barrels. Since it was a planned economic period, this series of paints was just used as theirs. The products used internally are not sold to the outside world, so the locks are not known to anyone. Today, these five models of paint have undergone nearly 20 years of baptism and continuous improvement in the market economy, and their performance has been greatly improved. The applied barrel factories have spread all over the country, and a large number of products are exported to overseas every year.