Characteristics and development status of fluorine

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Characteristics and development status of fluoro coatings for metal packaging

fluoro coatings have been more and more widely used in the field of metal packaging all over the world. Large containers, container barrels, small convenience barrels, metal cans and so on, have been extended to the whole industry of metal packaging. However, in China, the metal packaging products using fluorine paint are still very limited, which are mainly used for the internal coating of steel barrels. At present, fluorine paint has not been used for the internal coating of most steel barrels. Therefore, fluorine coating has made great progress and breakthrough in China's metal and plastic extruder market, and the packaging field still has a bright future

1 excellent characteristics of metal packaging fluoro coatings

in fluoropolymers, first of all, fluorine atoms replace hydrogen atoms and surround the carbon chain to form a tight protective layer, so that the carbon chain is not easy to be invaded by the outside world, and the whole molecular chain is hard and spiral; Secondly, there are a large number of C-F (460kj/MOI) bonds with high bond energy in the molecules, which are the main reasons for the thermal stability and chemical inertia of fluoropolymers

in addition, because the energy of visible light and ultraviolet light that destroy organic matter in solar energy cannot destroy the F-C covalent bond, so the polymer does not absorb visible light and ultraviolet light, and almost all of them pass through the fluoropolymer film, so that the film shows excellent weather resistance (when selecting pigments and fillers, we should choose super weather resistance, otherwise, the weather resistance of the whole fluoropolymer film will be affected by the factors of pigments and fillers themselves). Because of the excellent thermal stability, chemical resistance and super weather resistance of fluoropolymers, the development and application of fluoropolymers have been paid more and more attention. Fluoropolymers have been developed in the world and even in China for decades. However, the high crystallinity and difficult solubility of fluoropolymers developed in the early stage limit their practical application

2 classification and application of fluoro coatings for metal packaging

fluoro coatings are divided into powder coatings and liquid coatings (suspension, emulsion dispersion phase, solvent solution). However, according to the application situation in China, fluorocarbon coatings are divided into high-temperature curing fluorocarbon coatings and normal temperature curing fluorocarbon coatings

2.1 high temperature curing one carbon coating

high temperature curing fluorocarbon coating needs to go through the process of high temperature baking, dissolution and hardening. This kind of coating includes: polytetrafluoroethylene coating (PTFE), polytetrafluoroethylene coating (P,), polyvinylidene fluoride coating (PVDF)

optfe is mainly used in the coating of metal packaging with non sealing and low sanitary requirements, such as containers, food ton containers, etc. Opvf is resistant to various oils, acid, alkali, salt and pesticides, and is commonly used for coating the inner wall of steel drums and small packaging containers. For example, the force measurement of bulk oil, food and agricultural machinery sensors, digital display of force value, intuitive and clear, high measurement accuracy, automatic preservation of breaking force value, and the inner wall of drug packaging containers

● PVDF has super weather resistance, and its application in the field of large transportation packaging has the following advantages:

① the coating will not fade after long-term use; ② Excellent corrosion resistance: ③ good toughness: ④ excellent chalking resistance and stain resistance. 2.2 room temperature curing one carbon coating

Room Temperature Curing fluorocarbon coating is a fluoroethylene vinyl ether (ester) copolymer (FEVE) coating. Due to the introduction of -ci, -oh, -cooh and other active groups, the wax is not only easily soluble in solvents and can be cured at room temperature, but also improves its wettability with pigments and fillers, so that its application is widely promoted

3 current situation of fluorine coating for metal packaging in China

fluorine coating in China mainly includes high temperature curing and room temperature curing

high temperature curing fluoro coating mainly refers to PVDF. Due to the modernization construction and the improvement of living standards in China in recent years, some manufacturers in Jiangsu, Zhejiang and Guangdong have introduced foreign advanced metal plate production lines, which requires corresponding supporting fluoro coatings (PVDF). Now some large packaging containers are coated with this fluoro coating. However, the technical parameters of fluorine coating required by these metal plate production lines are harsh. In addition, most of the imported production lines meet the technical parameters of foreign fluorine coating, plus some other reasons, making this application field mostly the world of foreign products

domestic fluoro coatings mainly include powdered fluoropolymer from Shanghai organic Research Institute, polyvinyl fluoride coating from Zhejiang Chemical Institute, and PVDF from Shanghai sanaifu company. However, due to the long-term technical accumulation of these products and the copper limitation in spinning, these fluorocoatings are almost all room temperature cured. This is because the room temperature cured fluororesin has been industrialized and commercialized in this year or two. Plus advertising. It has become a new star in the paint industry overnight and a panacea for all kinds of film defects

however, domestic and foreign products are somewhat different according to their synthetic raw materials. For example, in Japan, the copolymer is synthesized from chlorotrifluoroethylene and alkyl vinyl aldehyde, and its structure is a strict alternating polymer; However, in China, chlorotrifluoroethylene and alkyl ethyl need to be prepared early, and it is difficult to get alternating polymers by taking alkenyl sugars to synthesize copolymers in advance. In addition, domestic resin products have a single model, and there are no industry and national standards. They are independent, and cannot provide a unified and ideal quality assurance for tree magic. For normal temperature curing fluororesin, people feel that it is highly commercial hype

4 problems existing in domestic fluoro coatings for metal packaging

in 2003, the annual consumption of high-temperature cured fluoro coatings in China was 1000 tons, and that of normal temperature cured fluoro coatings was 3oo tons. In the field of high-temperature fluorocarbon coatings, the development speed of domestic manufacturers is far lower than that of the domestic market. With the development of domestic packaging and other industries, the annual consumption of high-temperature PVDF has ranged from 0 to 1000 tons in five years, but domestic coatings have not yet seized the opportunity, and the market share is very low, which expands the detection range for Baotou Institute of quality control.

room temperature curing fluorocarbon coatings. The market has entered a state of disorder before it has been formed. High temperature curing fluoro coatings have been in operation for 30 years, but they still have considerable technical difficulties and complexities. Therefore, for the benefit of customers, foreign mainstream factories adopt strict quality commitment and guarantee system, that is, resin production enterprises issue use licenses to coating production enterprises, and coating production enterprises issue licenses to coating enterprises. On the one hand, the license promises product quality, on the other hand, it also promises to control the product quality of downstream customers. In this way, the end-user's quality commitment includes the guarantees and commitments of several enterprises, which is heavier and more persuasive

domestic enterprises, acting in their own way, have no unified standards and performance parameters, and do not provide technical support for coating enterprises. Although most of the products of the paint factory have undergone artificial aging tests, they do not pay attention to the communication with metal packaging enterprises, the collection and collation of outdoor exposure data, nor do they come up with convincing data and cases (the biggest feature of foreign products is the time-consuming accumulation of outdoor exposure to evaluate the coating performance)

at present, in the fluorine coating market, there is no foreign intervention in curing fluorine coating at room temperature. What is generally recognized in this market is the good performance of high-temperature fluorine coating, which users in the metal packaging industry have not really realized. In addition, the room temperature curing coating has greater technical randomness and construction difficulty, which is manifested in: the resin stability in the production process of tree wax is poor; Wide range of pigments and additives in coatings; There is no unified requirement for fluorine content (adding little fluorine is also called fluorine tree Eagle). Therefore, it is necessary to strengthen the basic research of resin on the one hand; On the other hand, cooperate with the coating industry and application parties to jointly check and maintain the superiority of fluorocoatings. At present, the urgent need is an industry standard - a common standard to be observed

source: organosilicon fluorine information

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