Coated iron and its application prospects

Coated iron and its application prospects

Liu Changsheng

1 Introduction

With the development of technology, consumption concepts and fashion, the competition between metal, plastic, paper and glass in packaging materials is becoming increasingly fierce. Metal packaging materials have always played an important role in the packaging field because of their good airtightness, hard texture, good elasticity, good light resistance and good gas barrier properties. Especially for meat, vegetables and other products, metal containers are still the first choice. . As an important part of metal packaging materials, tinplate plays an important role in food, beverage, aerosol cans and chemical tanks. However, as tin is the main strategic resource, the price is more expensive, and the resources are increasingly exhausted. Therefore, chrome-plated iron, coated iron and powder electrophoresis products are increasingly used as substitutes for tin-plated and low-tin plates. attention.

2 Production process and product characteristics of coated iron

2.1 Production process of coated iron

The coated iron is a multi-layer polyester composite film (thickness of about 20 to 25 μm) which is covered (bonded) on both sides of a cold-rolled steel sheet (generally a coiled steel sheet)/chrome-plated iron, and is a plastic film and A metal functional material with a dual feature of sheet metal. Theoretically, the coated iron substrate can be directly used as a cold-rolled steel sheet, that is, the iron is left. The color film leave-on-film technology is unique in China. However, when the iron-coated cans are left, the weld seams of the cans are prone to rust and the adhesion is not strong. In Europe, America and Japan, the coated iron technology is mostly used. The chrome-plated iron TFS is used as the substrate, that is, it is not suitable to leave the coated iron. The adhesion of the organic film is extremely high, mainly due to the presence of a chromium hydrated oxide film on the surface of the TFS product, which is combined with the organic film in the form of hydrogen bonds, as shown in FIG. Figure 2 is a film line directly attached to the ECCS plating section.

Figure 1 Schematic diagram of the combination of TFS substrate and organic film

At present, there are two kinds of laminating processes: one is the extrusion process under high temperature and high pressure. Using high temperature coating and rapid recrystallization, the adhesion of organic film is very high (this process is widely used in Europe and the United States and Japan); the second is the bonding process, which uses low temperature bonding, and its bonding fastness is not as high as high temperature. High pressure method.

2.2 Features of coated iron

Compared with paint iron (ie, tinplate (chrome-plated iron) printed on the outer surface), the coated iron has the following characteristics:

(1) It has good functions of anti-rust, decoration, heat insulation, shock absorption, etc., especially stamping and corrosion resistance is unmatched by coating iron. Since the film covered (bonded) by the coated iron is a multi-layered polyester composite film, its ability to block the penetration of corrosive media is close to "complete repression". For the packaging of ketchup pots and two-piece cans, coated iron is an ideal material. There is a contradiction between the corrosion resistance and the adhesion of the coating iron.

Figure 2 Thin film layer line connected to the ECCS plating section
1-unwinder; 2-looper; 3-ECCS section; 5-looper; 6-coating wax; 7-coiler

(2) The surface pinhole is small, dense, and can be processed on the film, such as marking, laser treatment, etc. (compared with the coating). For the secondary cold-rolled coated iron (also known as "Mane board" abroad), it has excellent mechanical properties and high tensile strength. Table 1 compares the performance of secondary cold rolled coated iron with secondary cold rolled ordinary tinplate.

Table 1 Comparison of performance between secondary cold rolled coated iron and secondary cold rolled ordinary tinplate

As can be seen from Table 1, the elongation of the manne plate at the hardness of DR-8 is 10%, while that of the ordinary plate is 3%. According to reports in the literature, the reason why the mane board is high in hardness and good in elongation is the vacuum smelting in steelmaking, which greatly reduces the content of certain non-metallic elements (including carbon) and certain metal elements in steel. (10 to 5).

(3) High production efficiency, low energy consumption and material cost. The surface of the coated iron is a thermoplastic resin film, and the polyester represented by polyethylene terephthalate (PET) and the resin represented by polypropylene (PP) are preferably used, and the film formation temperature is only about 70 ° C, and there is no need for internal Coating external printing, production efficiency and energy consumption are ideal; in addition, the coated iron substrate does not need to use tinplate as a substrate, which is obvious in the current situation of the surge in price and resource shortage of tinplate.

(4) Conducive to environmental protection. The inner coatings of paint iron are mainly epoxy resin, and the outer coatings are base paint, white paint and glazing paint. The main products are acrylic acid and polyester resin. The printing ink has thermal curing and ultraviolet curing (UV), but the printing ink must be matched with the coating to ensure the color and adhesion of the ink. Since the currently used coatings are added to the organic polymer by adding a curing agent, a plasticizer, a toner, and the like, and are dissolved in a solvent and a diluent, there is still an environmental problem in the printing iron factory to be solved. In addition, for ketchup cans, deep-drawing two-piece cans, etc., the coating iron is not stable enough. The coated iron with a thermoplastic resin film on the surface does not have a large amount of solvent exhaust gas during the production process, which is environmentally friendly.

3 Development status of coated iron

After the 1990s, TFS products, one of the tinplate substitutes, were widely used in the United States and Japan. Its main purposes are: crown cap, four-turn cap; three-piece can top and bottom cans; canned edible oil, canned condiments; solid shaped food, tea, detergent and other common containers; internal combustion engine fuel oil, paint, Paint cans, etc. However, TFS products have two shortcomings: First, the protective coating film needs to be applied on both sides of the product, and the printing process causes serious benzene pollution to the environment and humans; second, some coatings have unavoidable trace residues. , affecting human health.

Therefore, in the late 1980s, Japan successfully produced coated iron with chrome-plated iron as a substrate. However, the product could not be deep drawn at the beginning of the product launch, and the cost difference between the DI tank and the DI tank was large, and the market demand was limited, so it was not widely used. At present, this technical problem has been solved perfectly, and the advantages of coated iron have also been widely recognized by users. The production of coated iron is increasing rapidly. At present, Japan has 5 coated iron production lines, 3 Toyo Steel Co., 2 Nippon Steel Corporation and 1 JFE Company, with a total capacity of 600,000 t/a. In 2005, the actual production of coated iron in Japan was 490,000 tons, accounting for 60% of TFS production. Since the 1990s, Germany, Britain, the United States, France and other countries have successfully developed coated iron that can completely replace tinplate, which accounts for a large proportion of the total consumption of tinplate. With the shortage of tin resources and harsh environmental requirements, it has forced the rapid development of coated iron in recent years. Table 2 shows the production of coated iron in Asia and Europe at the beginning of 2005.

Table 2 Production of coated iron in Asia and Europe at the beginning of 2005 (unit: 10,000 tons)

At present, China's coated iron production is in its infancy, there are two companies: First, a privately owned enterprise in Wuxi, with three production lines, using cold-rolled sheets as the coated substrate, using a bonding process, with an annual output of 20,000 tons. The production line speed is 80m/min, and the adhesion between the film and the substrate is not as good as that of foreign countries. Secondly, a coated iron production line introduced by Shanghai Desheng Lianxing Co., Ltd. in 1998, although its product quality and appearance are superior to the same type of three-piece beverage. Can products, but because of the high cost of the product, there is no competition at all, the production line has not been able to start effectively since its introduction. It can be said that the TFS substrate coated iron required by the market has no localization ability. The cold-rolled sheet mill of Baosteel Co., Ltd., which has the fastest, the thinnest and the most advanced chrome-plated iron production line in China, has the conditions for producing coated iron by high-temperature and high-pressure extrusion process using chrome-plated iron as a substrate. The construction plan of the coated iron production line.

As the competition for food packaging materials becomes more and more fierce, the trend of steel-based metal materials used in the canning industry is declining. The secondary cold rolling technology can reduce the thickness of the cold rolled sheet, increase the utilization rate of the steel, and achieve the purpose of reducing the cost, thereby improving the competitiveness of the steel can. At present, Baosteel Co., Ltd. cold-rolled sheet plant has secondary cold rolling technology, the product thickness specification is 0.15 ~ 0.36mm, the thinnest can reach 0.10mm. The specifications of foreign users are generally much thinner than those of domestic users. Currently, developed countries have used very thin steel plates with thicknesses of 0.07 to 0.12 mm to make barrels and cans. The foreign market share of Baosteel's secondary cold-rolled products has also reached more than 20% and is growing. For the secondary cold-rolled coated iron, due to the increasing demand for two-piece cans for food, Corus Group and Crown Co., Ltd. jointly studied the second coating. Adaptability issues between cold rolled sheets and existing equipment. Represented by the French Lorraine Sheet Plant, it has produced a second cold-rolled coated iron with excellent elongation, which is very suitable for two-piece stamping cans and easy-opening covers.

4 Status and prospects of domestic and foreign application of coated iron

At present, coated iron has a good application prospect in the packaging materials market such as two-piece cans such as punching tank DRD, punching cup DI, shaped cans, Easy Opened End and Easy Peeled End. It also provides packaging materials for individualized and fashionable consumption concepts for food cans, various beverages, oleochemicals, daily chemicals, medical and health industries.

In the foreign coated iron market, there is a large amount of coated iron that should not be left blank. When the coated iron can is used, dry molding can be used without excessive lubricant, which can avoid polluting the environment by generating a large amount of waste water by cleaning the lubricant. As a result, a wide variety of stamping tank DRDs (and cupping DI) are becoming more popular. For example, coated iron coated with polyethylene terephthalate (PET) and polypropylene (PP) can be used to make caps for caps, DRD cans and sprayers, etc.; coated iron with polyester film has excellent properties. Processing adhesion and processing corrosion resistance, suitable for making deep-drawn cans and welding cans with large deformation and high corrosive materials. At the same time, the polyester film coating has a small absorption rate of food, and can make food in the can. The various components in the composition maintain a delicate balance and make it in good shape for a long time. The three-piece cans have been gradually reduced in developed countries due to the complicated production, and instead, the stamping cans DRD and the cupping DI are used. Japanese steel two-piece cans (DI and TULC) have a market share of 60%.

In recent years, easy-to-tear covers have gradually gained popularity in foreign countries. The cover is actually a secondary cold-rolled steel sheet or a secondary cold-rolled aluminum sheet coated with a thickness of 0.07 to 0.13 mm, which is cleverly sealed on an empty can by mechanical and heating techniques, and is peeled off when used. Certain types of EPE can withstand high temperature sterilization. From the perspective of Europe and the United States, the technology of coated aluminum is more mature than coated iron. However, the cost of the steel easy to tear cover is only 50% of the easy opening of the aluminum. Therefore, the coated iron easy to tear cover is a direction for future development.

Impress Holding, the world's largest canmaker, owns a factory with an annual output of 1.4 billion canned fish in Germany, 70% of which use coated aluminum cans. Crown has four production plants in France and Italy, mainly producing canned meat (5 million cans/a) and also using coated aluminum. It can be seen that with the development of coated iron technology, enterprises aiming at maximizing profits will tend to replace low-cost coated aluminum with high-cost coated aluminum.

At present, the application of coated iron in China's two-piece cans is still in its infancy. With the rapid expansion of the two-piece can application in the world, it has greatly promoted the market demand for two-piece cans in China. At present, the annual consumption of two-piece cans (steel and aluminum) is about 10 billion. Calculated at a rate of 10% per year, after five years, the demand for two-piece cans in China will reach 16 billion, a net increase of 6 billion. At present, the domestic steel two-piece can production is about 1.2 billion, the occupancy rate is only 12%, the capacity is insufficient and the energy consumption of the traditional D1 can production process, the secondary pollution problem and its inherent disadvantages (affecting the flavor can not enter the beer) The market, easy to rust) limits its further development. Therefore, it can be foreseen that the domestic market prospect of making two-piece cans with green and coated iron is very broad.

As environmental protection requirements become more stringent and resources become scarcer, recyclable and recycled metal packaging materials are favored by people. According to the European Association of Packaging Iron Manufacturers, the recycling rate of steel packaging in the 15 countries of the European Community reached 61% in 2003 (of which Belgium has reached 94%), and by 2008, it will increase to 70%. Therefore, the global canning material industry, canning industry and cap manufacturing industry are undergoing revolutionary major changes, secondary cold rolled sheet, coated iron (coated aluminum), stamping cans, punched shaped cans and easy to tear. The cover is slowly becoming the mainstream of the can manufacturing industry in developed countries. The key (basis) of these changes is the advancement of secondary cold rolled sheet quality (advancement in steelmaking technology) and the development of laminating technology.

Baking Molds

Baking Molds,Silicone Baking Molds,Silicone Cake Molds,Mini Cake Pans

Yangjiang Yado Kitchen Industry Co., Ltd. , https://www.yadokitchen.com