Steel barrels have achieved major technological breakthroughs

Over the years, there have been a lot of problems in China's steel drum special interior coatings, and it has been difficult in terms of technology and quality to compare with foreign advanced steel drum coatings to make the inner steel drums in a long-term, low-level, high-accident situation. The main problems in China's steel drum paints are poor corrosion resistance and hygienic performance, and poor construction performance. This prevents the quality of inner steel barrels used to hold special chemical raw materials, medicines, and foods from being guaranteed. The accidents are endless and severely restricted. The normal packaging, storage and export trade of our products.

Recently, Shanghai XCMG Coating Technology Co., Ltd. developed and produced a special epoxy coating for X-622 steel drums. The product has passed the FDA food and drug coating testing. This is the only special coating for steel barrels in China that has obtained FDA food and drug coating certification, laying a solid foundation for the international market for steel barrels in China. At present, the paint has become the only steel drum inner coating (patent number: ZL01 2 45930.5) that has obtained the national patent in China, and has begun mass production and put into the market. It has been welcomed by many domestic barrel manufacturers.

Shanghai Xugong Coatings Technology Co., Ltd. is a three-unit restructuring of Shanghai Steel Bucket Technology and Equipment Research Institute, Shanghai Huagong Packing Container Co., Ltd. and the coating workshop of Shanghai Chemical Co., Ltd., which was established in 1931. It is a steel drum in China. The only professional company in the industry that specializes in the research, development and production of various types of steel barrels, such as normal-temperature and quick-drying internal and external coatings, baking-type internal and external coatings, instant paint removers, degreasing liquids, phosphating solutions, and foamed steel barrel sealants. .

Xu Guoxing, director of the former Shanghai Steel Bucket Technical Equipment Research Institute, has been engaged in the research of steel drum equipment and steel drum technology, steel drum coating and steel drum coating for more than 30 years. He has rich practical experience and solid theoretical foundation; There are more than 50 papers published in newspapers and magazines, and many technical presentations have been held at national and pan-Asian steel drum conferences. His research team won the Shanghai model group in 1982 for inventing the A-22 type textile pulp. He developed the X-622 epoxy coating and won the Shanghai Chemical Drum Factory Technology Innovation Award. In January 1989, he successfully developed the X-622 epoxy coating. X-891 coating has become the only patented product in China's steel drum coating.

The company owns the strong technical strengths of the original two institutes and the entire coating production equipment of the Shanghai Chemical Cooperage Factory paint shop, plus the original professional research institute for steel drum manufacturing companies and steel drum technology. The research and manufacturing can be carried out with great effort and excellence. The paint produced can be more suitable for steel reeds and steel barrels. The application of paint can better suit the coating process of steel barrels and can be adapted to the drying of steel barrels. In baking conditions, the formed coating can be more adapted to the pressing and forming of the size of the lid, and is more suitable for the curling process of the bottom lid and the barrel when the steel drum is sealed.

Because the original two research institutes did a lot of research, testing and trial work on the paint according to the characteristics of the steel drum itself, and did a lot of corrosion-resistant immersion tests, the paint produced was completely fitted to the coating of steel drums. Steel drums coated with the company's coatings have a smooth, high-adhesion, high impact resistance and a wide range of suitability.

At present, domestic paints used extensively in the domestic steel drum industry are mainly classified into three categories: epoxy, PVF, and phenolic.

Epoxy coating is the earliest use, but also the best cost-effective domestic and foreign steel drum industry is still commonly used in traditional coatings. Epoxy coatings produced in China have a solid content of about 36%. The organic volatiles are mainly xylene, cyclohexanone, alcohols and esters; the X-622 steel drums have a solids content of about 40% for epoxy internal coatings. Its organic volatiles already contain no xylene.

PVF coatings are much more viscous than other coatings. In fact, its solids content is only about 24%. The organic volatiles are mainly dimethyl phthalate, propylene carbonate and the like.

Phenolic steel drum coating is currently only X-362 type, its viscosity looks very low, only about 20 seconds (paint -4 cup 25 °C), but its solid content is also up to about 40%, the main organic volatile matter Ketone alcohols. As a result, the environmental pollution of the interior paint during construction is reduced, and the production cost is effectively reduced.

The X-362 steel drum coating is a special thermosetting phenolic resin coating for steel drums. Compared with the general phenolic resin coating, it has greatly improved the adhesion of the steel drum plate, the bending resistance of the coating, and the storage period of the coating.

Phenolic resin is one of the earliest and first industrialized products found in synthetic resins and one of the best anti-corrosion materials. Thermosetting phenolic resin is a macromolecule synthetic resin formed by polycondensation of phenol and aldehyde under the action of a basic catalyst. It has an active hydroxymethyl group on the benzene ring at a high temperature and can be crosslinked with an excessive amount of formaldehyde in the resin. Dense, stable coating with a mesh structure. Therefore, its anti-mildew, anti-corrosion, moisture, oil, solvent, salt spray, chemical resistance and excellent performance, and can withstand any concentration of hydrochloric acid and a variety of organic acids and pesticides, ammonia, surfactants and other items. Moreover, after high-temperature cross-linking, the methylene bond in the phenolic resin has fairly stable properties, so its heat resistance is better than that of epoxy resin and unsaturated polyester resin, and it can even be used at 120° C. for a long period of time.

However, due to the presence of benzene rings in its molecular structure, nitration and sulfonation reactions can occur, so it is not resistant to strong oxidizing acids such as concentrated sulfuric acid and nitric acid. In addition, due to the presence of phenolic groups in the structure, the hydroxy group on the benzene ring has a weak acidity, and its hydrogen can be replaced by sodium to form a water-soluble sodium phenolate product, so the alkali resistance is poor, and it is also not resistant to the melted phenolic products.

The general thermosetting phenolic resin coating has a benzene ring structure due to the curing cross-linked body, so the coating film is very brittle, and the coating is fractured by bending the coating slightly, and the shelf life is only about 3 months at about 20°C. However, because X-362 coating is specially designed for steel drums and is a special inner coating for steel drums that has been improved on the basis of thermosetting phenolic resins, it takes into account the bending of the steel drum when the bottom cover is rolled and on the steel drum. The plate is attached and leveled. Its coating on tinplate can be bent to more than 90°. Its storage period can be as long as one year. X-362 coatings are available in reddish-brown transparent and yellow coatings with excellent coating properties (it can be said that in addition to poor alkali and oxidation resistance acid properties, other anti-corrosion properties are superior to PVF coatings and epoxy coatings), and spraying The unit consumption is also relatively low. The coating per kilogram of X-362 steel drums can be sprayed with more than 8 steel drums of 200 liters. In addition, it has great advantages in terms of price, so it has long been widely used in inner coating of steel drums. .

The spray viscosity of the X-362 steel drum coating should be lower, preferably about 12 seconds (-4 cups, 25°C). The coating should also be thin, otherwise it may cause foaming of the coating during baking. The curing conditions for the standard oven were 190°C for 45 minutes and the reference baking conditions were 220°C for 15 minutes. Specifically, the optimum baking temperature and baking time can be determined according to different baking equipment after the test.

The successful development of a new type of drum paint has undoubtedly greatly improved the quality of the inner steel drums in China, and the production cost has been effectively reduced. Moreover, the environmental pollution caused by the production of painted steel barrels has also been greatly reduced. This is a major step forward for China in the realization of green packaging.

Source: China Packaging News