ã€Abstract】The excellent properties, classification and application of fluorine coatings were introduced. The current status of fluorine coatings in China and some problems in the development of fluorine coatings at home and abroad were discussed.
[Keywords] current status of fluorine coating
1 Characterization of Excellent Properties of Fluorine Coatings
In fluoropolymers, fluorine atoms are first substituted for hydrogen atoms and surround the carbon chain to form a close protective layer, making the carbon chain less vulnerable to external attack and making the entire molecular chain harder and spiraling; There are a large number of high-energy C-F (460KJ/MOL) bonds, which are the main reasons for the thermal stability and chemical inertness of fluoropolymers.
In addition, due to the energy of visible light and ultraviolet light that damage organic substances in solar energy, it is impossible to destroy the F-c covalent bond. In this way, the polymer does not absorb visible light and ultraviolet light, and almost entirely passes through the fluoropolymer film. The coating film exhibits excellent weather resistance (in selecting an amount of filler, 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 development of fluoropolymers in the world and even in China has a history of several decades. The earliest examples are: DuPont's Teflon PTFE. However, the high crystallinity and insolubility of fluoropolymers that were developed early limited their practical application.
2 Classification and Application of Fluorine Coatings
Fluorine paints are divided 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 fluorocarbon coating
High-temperature curing fluorocarbon coatings require high-temperature baking, dissolution, and hardening processes. The coatings include: PTFE coating, PvF coating, and polyvinylidene fluoride coating (PvDF).
â— PTFE is mainly used in non-stick pans, microwave ovens, barbecue machines, baking and biscuit machines, etc. The most obvious example is DuPont's Pfluron products.
â— PvF is resistant to all kinds of oils, acid salts and pesticides. It is commonly used for the inner wall coating of containers. Such as bulk oil, food and pesticide packaging container wall. China's Zhejiang Chemical Industry Institute exports a large number of fluorine-containing products every year, that is, PvF.
â— PvDF has super weather resistance, and has the following advantages in the field of construction:
1 long-term use of the coating does not fade; 2 excellent corrosion resistance; 3 toughness; 4 excellent resistance to chalking and stain resistance; such as: Daikin's kynar-500.
2.2 room temperature curing fluorocarbon coating
Room-temperature curing fluorocarbon coatings are vinyl fluoride-vinyl ether (FEVE) coatings due to the introduction of -CL, -OH, -C00H, etc.
The groups make the resin not only soluble in the solvent, but also can be cured at room temperature, and the wettability with the front filler is improved, so that the application of the resin is widely promoted. The most representative is the product launched by Asahi Glass in Japan in 1983. It has been tested in bridges and chemical plants in 24 places in Japan. After more than 20 years of testing, its application areas are mainly distributed in: 1 building construction and Outside the factory; 9 outdoor structure; 2 vehicles; 4 steel structure anti-corrosion.
3 Status of China's Fluorine Coatings
China's fluorine coating mainly includes high temperature curing and room temperature curing.
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 aluminum alloy sheet production lines, which require corresponding supporting fluorine coatings ( That is, PvDF), which is currently coated with the outer layer of high-rise curtain wall aluminum alloy panels in some cities. However, these aluminum alloy plate production lines require fluorine coatings, technical parameters are harsh, in addition to the introduction of most of the production line to meet the foreign fluorine coating technical parameters, plus other reasons, making this application mostly foreign products world.
Domestic fluorine coatings mainly include powdered fluoropolymers from Shanghai Organic Institute, polyvinyl fluoride coatings from Zhehua Institute, and PvDF from Shanghai Aifu. However, due to the long-term technical accumulation of these products, and because of construction restrictions, these fluorine coatings are almost all room temperature curing type. This is because the industrialization and commercialization of room-temperature curing fluororesin in this year and two years, together with the ad propaganda of advertisements, made it fierce overnight and became a new star in the coatings industry. It also became a panacea for the treatment of various types of film defects.
The basic route for the curing of these normal temperature and medium temperature curing type fluorocoatings is as follows:
Based on fluororesin + curing agent (normal temperature curing)
Fluoro resin + melamine (low temperature baking)
However, according to its synthetic raw materials, domestic and foreign products are somewhat different. For example, in Japan, a copolymer is synthesized from chlorotrifluoroethylene and alkyl vinyl ether. Its structure is a strictly alternating polymer; in China, it is synthesized from trifluoroethylene and alkyl vinyl ester. It is difficult to get alternating polymers (some manufacturers reported that the formulas were from one). In addition, domestic resin products are of a single type, and there are no industry and national standards, and they are independent of one another and cannot provide a unified and ideal resin quality assurance. For normal temperature curing type fluororesin, I have contacted several manufacturers. The general feeling is that commercial hype is very strong. At the second exchange meeting, a unit claimed that its fluorine coating could be used for 20 years, and was linked with the development of the western region, such as: West-East Gas Transmission, three horizontal and two longitudinal traffic barriers, Qinghai-Tibet Railway, Leshan Giant Buddha Relics Restoration, Western Airport Construction and so on. But when we come up with specific questions, we cannot answer them. Another company, at the meeting, took out two test reports, one for the Institute, and the other for Shanghai Jiaotong University. The fluororesin that was claimed to be produced was a new generation product of the country and was recognized by many experts. However, the information obtained from a test is the same as what the other party's resin is not seen. It feels that the current market is more speculative than the fluorine coating, and it really does not do much work. In particular, there was a strange phenomenon at this meeting. China's resin and paint manufacturers desperately praised the superiority and the beauty of fluorine coating at the meeting, while well-known foreign companies, including Asahi Glass, Daikin, and San M Co., Ltd., were pouring cold water. Seriously introduce the failure of the project, such as the external wall of HSBC.
4 Some confusion in the development of domestic and foreign fluorine coating market
In 2000, the annual dosage of high-temperature-cured fluorocoatings in China was 1000t, and the annual dosage of room-temperature-cured fluorocoatings was 300t. 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 the domestic aluminum curtain wall fluorocarbon spraying industry, its annual consumption from 0 to 1000 tons in 5 years, but the domestic painters did not seize the opportunity, the market share is very low.
Normal-temperature curing fluorocarbon coatings enter the disorder when the market has not yet formed. High-temperature curing fluorine coatings have been operating for 30 years, but still have considerable technical difficulties and complexity. Therefore, foreign mainstream plants adopt strict quality commitments and safeguard systems for the benefit of their customers. It is the resin coating production enterprise that issued the license for use by the resin production enterprise, and the coating production enterprise grants the license to the coating company.
The license on the one hand promises product quality. 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. In this way, large projects can each exert their respective advantages to ensure the implementation of the project. This core and bond is that everyone follows the product quality standards (that is, AAM605.2, AAMA2605 standards of the American Building Society), so that in large projects, Party A can clearly demand; a certain resin, a kind of paint and a certain Painting factory support to ensure their own interests.
Domestic enterprises, each with its own politics, do not have uniform standards and performance parameters, nor 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 coating 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. The time-consuming accumulation of the exposure was used to evaluate the properties of the coating, such as: the US AAMA 2605 requirement is 10 years, and the Japanese JISK 54009.9 requirement is 3 years).
At present, the fluorine coating at normal temperature in the fluorine coating market has not been introduced from abroad. This market is generally recognized as the good performance of high-temperature fluorine coating. This point, users do not really understand. Overseas Asahi Glass Co., Ltd. has 20 years of experience in production and promotion. Once introduced, it will provide a complete set of products and technical services. In addition, room-temperature curing coatings have greater technical arbitrariness and difficulty in construction. This is manifested in: poor resin stability in the resin production process; wide range of pigments and auxiliaries in the coating; no uniform requirement for fluorine content (plus little fluorine Also called fluororesin). 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 pressing need is an industry standard - a common standard.