In the world of
Metal Packaging, the application of fluorine coatings has become more and more extensive. As large as containers, container drums, small buckets, metal cans, etc., the use has expanded to the entire industry of metal
Packaging. However, in China, the use of fluorine coating metal packaging products is still very limited, mainly used for steel barrels. Internal coating, and most of the current internal coating of steel barrels have not used fluorine coating. Therefore, fluorine coatings have a promising future in the field of metal packaging in China.
1. Excellent Characteristics of Metal Packaging Fluoropolymer In fluoropolymers, fluorine atoms are first substituted for hydrogen atoms, and they are surrounded by carbon chains to form a close protective layer, making the carbon chain less vulnerable to external attacks and making the entire molecular chain more difficult. Hard, spiral; followed by a large number of high bond energy cF (460kJ / moi) bond, these are the main reason for the thermal stability and chemical inertness of fluoropolymers.
In addition, since the energy of visible light and ultraviolet light that destroys organic substances in solar energy cannot destroy the F-C covalent bond, the polymer does not absorb visible light and ultraviolet light, and almost completely passes through the fluoropolymer film. The coating film exhibits excellent weather resistance (When a pigment filler is selected, super weather resistance is selected, otherwise, the pigment filler itself affects the weather resistance of the entire fluoropolymer film). Due to the excellent thermal stability, chemical resistance and super weatherability of fluoropolymers, the development and application of fluoropolymers are increasingly valued. The world and even our country have developed fluoropolymers for decades. However, the high crystallinity and insolubility of fluoropolymers that were developed early limited their practical application.
2. Classification and Application of Metal Packaging Fluorine Coatings Fluorine coatings are classified into powder coatings and liquid coatings (suspensions, emulsion dispersions, solvent solvents). However, according to the use of our country, the fluorine coatings are divided into high-temperature curing fluorocarbon coatings and room temperature curing fluorocarbon coatings.
2.1 High-temperature curing One-carbon coating high-temperature curing fluorocarbon coatings need to be baked, dissolved, and hardened at high temperatures. Such coatings include: PTFE coating, PVF, and PVDF coating.
OPTFE is mainly used in the fields of non-sealing and coating of metal packaging with low hygiene requirements, such as containers and food containers. OPVF is resistant to all kinds of oils, acid and alkali salts and pesticides. It is commonly used for the inner wall coating of steel drums and small packaging containers. Such as bulk oil, food and pesticide packaging container wall.
PVDF has super weather resistance, and has the following advantages in the application of large-scale transport packaging:
1 long-term use of the coating does not fade; 2 excellent corrosion resistance: 3 good toughness: 4 excellent resistance to chalking and stain resistance. 2.2 Normal-temperature curing One-carbon coating room-temperature curing fluorocarbon coating is a fluoroethylene monovinyl ether (ester) copolymer (FEVE) coating, and the introduction of -Ci, -OH, -COOH and other active groups makes the tree wax not only soluble In the solvent, it can be cured at room temperature, and the wettability with pigment fillers is improved, making its application widely popularized.
3. The status of China's metal packaging fluorine coating China's fluorine coating mainly includes high temperature curing and room temperature curing type.
High-temperature-curing Fluxetritol mainly refers to PVDF. Due to China's modernization and improvement of living standards in recent years, some manufacturers in Jiangsu, Zhejiang, and Guangdong have introduced foreign advanced metal sheet production lines, which require corresponding supporting fluorine coatings (ie, PVDF), which is now coated with the outer layer of some large packaging containers. However, the fluorine coatings required by these metal plate production lines are technically demanding. In addition, most of the imported production lines comply with the foreign fluorine coating technical parameters, plus other reasons, making this application area mostly dominated by foreign products.
Domestic fluorine coatings mainly include powdered fluoropolymers from Shanghai Organic Institute, polyvinyl fluoride coatings from Zhejiang Chemical Industry Institute and PVDF from Shanghai San Aifu. However, due to the long-term technical accumulation of these products, and due to the restrictions on copper in the rotation industry, these fluorine coatings are almost all room temperature curing type. This is because the two-year room temperature curing fluoroplastic industrialization, commercialization. Plus advertising campaign. It made it a fierce night and became a new star in the paint industry. It also became a panacea for all kinds of film defects.
However, according to its synthetic raw materials, domestic and foreign products are somewhat different. For example, in Japan, copolymers of chlorotrifluoroethylene and alkyl vinyl aldehydes are synthesized, and the structure is a strictly alternating polymer; while in China, chlorotrifluoroethylene and alkyl vinyl saccharides are used to synthesize copolymers. Hard to get alternating polymers. In addition, the domestic resin product models are single, there is no industry and national standards, and they are independent of each other, and they cannot provide a unified and ideal tree magic quality assurance. For normal-temperature curing fluoro-tree wax, it gives a feeling that commercial hype is very strong.
4. Existing Problems in Domestic Metal Packaging Fluorine Coatings In 2003, the annual amount of high-temperature-cured fluorocoatings in China was 1,000 tons, and the annual amount of room-temperature-cured fluorinated coatings was 30%. In the field of high-temperature fluorocarbon coatings, the speed of development of domestic production enterprises is much lower than that of the domestic market. High-temperature PVDF With the development of domestic packaging and other industries, its annual consumption is from 0 to 1,000 tons in 5 years, but domestic coatings have not yet seized the opportunity and the market share is very low.
Room temperature curing fluorocarbon coating. If the market has not yet formed, it will enter a disorderly state. High-temperature curing fluorine coatings have been operating for 30 years, but still have considerable technical requirements of difficulty and complexity. Therefore, in order to benefit the customers, foreign mainstream plants adopt a strict quality commitment and guarantee system. The resin production enterprises issue licenses to coating production companies, and coating production companies grant licenses to coating companies. On the one hand, the license promises product quality, and on the other hand, it also promises to control the quality of downstream customers' products. This way, the end-user quality commitment includes the guarantees and commitments of several companies, which are heavier and more convincing.
Domestic enterprises do not have uniform standards and performance parameters, nor do they provide technical support for coating companies. Although most paint products of the paint factory have undergone artificial aging tests, they do not pay attention to communicating with metal packaging companies and do not pay attention to the collection and arrangement of outdoor exposure data, and they do not have persuasive data and cases. The most important feature of foreign products is the use of outdoor products. This time-consuming accumulation of exposure to evaluate paint performance).
Currently in the fluorine coating market at room temperature curing fluorine coating, no foreign intervention, this market is generally recognized is the good performance of high-temperature fluorine coating, this metal packaging industry users did not really appreciate. In addition, room-temperature curing coatings have greater technical arbitrariness and difficulty in construction. This is reflected in the poor stability of the resin in the production process of tree wax, the wide range of pigments and additives in the coating, and the lack of uniform fluorine content (plus few Fluorine is also called Fluorescent Hawk. Therefore, it is necessary to strengthen the basic research of the resin on the one hand; on the other hand, it is necessary to cooperate with the coating industry and the application side to ensure the superiority of the fluorine coating itself. The current urgent need is an industry standard - a common standard.
