The generation of electrostatic spraying, so that the surface treatment of aluminum curtain wall panels to be resolved, not only so that the color difference becomes smaller and can get a variety of colors of aluminum panels. Electrostatic spraying is divided into: powder spraying and fluorocarbon spraying, powder spraying raw materials are: polyurethane, polyurethane resin, epoxy resin, hydroxy polyester resin and epoxy/polyester resin, can be formulated in a variety of colors. Characteristics of powder spraying: spraying equipment has manual, automatic hanging type, construction is simple, the coating thickness of 30 microns or more, impact resistance, abrasion resistance, corrosion resistance, weather resistance, etc. are good, the price of paint is cheaper than fluorocarbon. The biggest weakness of powder spraying is afraid of the sun's ultraviolet radiation, long-term irradiation will cause natural fading, aluminum sunny side and non-sunny side after a few years the color difference is obvious, generally 2-5 years on the production of obvious color difference. Now on the market appeared in the name called colored aluminum profiles, used for aluminum doors and windows, is sprayed with ordinary aluminum powder. Aluminum doors and windows to increase the variety of colors, but also to enhance corrosion resistance.
Another electrostatic spraying for liquid spraying, also known as fluorocarbon spraying, Hong Kong is called curium oil. Belong to the high-grade spraying price is high, in foreign countries have long been applied. In the last two years in the country only a large area for aluminum curtain wall, due to its excellent characteristics, more and more by the construction industry and the user's attention and favor. Fluorocarbon spraying has excellent anti-color fading, frost resistance, corrosion resistance to atmospheric pollution (acid rain, etc.), strong UV resistance, strong resistance to cracking as well as the ability to withstand harsh weather conditions. It is not as good as general coatings.
I, fluorocarbon spraying raw materials and structure
Fluorocarbon spray coating is a polyvinylidene fluoride resin nCH2CF2 baking (CH2CF2) n (PVDF) for the base material or with metal aluminum powder for the color of the paint. Fluorocarbon base material in the chemical structure of fluorine / carbonization bond. This structure with short bonding properties and hydrogen ion bonding is considered the most stable and strongest combination, and the stability and firmness of the chemical structure makes the physical properties of fluorocarbon coatings different from those of general coatings. In addition to the mechanical properties of abrasion resistance, impact resistance has excellent performance, especially in harsh climates and environments show long-lasting anti-color fading, anti-ultraviolet performance. In the early sixties, it began to be used in engineering plastics for wires and cables. In 1965, Pennwalt Chemical Company in the United States firstly synthesized polyvinylidene fluoride as the base material and aluminum powder with metal particles to form the architectural overcoat paint, also known as metal paint, and took Kynar500 as the trademark. As a result, the world's manufacturers have begun to use Kynar500 to manufacture their own fluorocarbon paint overcoat paint to meet the high-grade building interior and exterior aluminum coating, a wide range of color choices, beautiful and dignified appearance, and durability for the world's many magnificent curtain wall buildings to add luster. Coating manufacturers of the coating life of the guarantee began to 10 years, 15 years to ensure the development of 20 years.
American research institutions have fluorocarbon coatings and super coatings, general coatings have been tested and compared, respectively, coated samples placed in the U.S. Florida scorching sunlight, as well as in the humid air containing salt in the harsh environment exposed to 12 years, the actual proof of fluorocarbon coatings, stability and durability than the other two types of coatings higher than 30 and 80%, fluorocarbon coatings ensure that the harsh environment in a variety of The fluorocarbon coatings are guaranteed to be used in a variety of harsh environments.
Many fluorocarbon coating manufacturers around the world generally use Kynar500 or Hylar5000 as the base material for neon carbon coatings. There is no regular certified manufacturer in China. The main manufacturers of fluorocarbon coatings are:
1. 1CI, UK;
2. PPG, USA;
3. Valspar, USA;
4. DNTSingapore (Dai Nippon Paint Singapore);
5. Kawsai, Japan;
5. Japan Kawsai (Kansai) Coatings Company;
6. Korea Koreachemical Company;
7. Taiwan Fengyuan Paint Company;
Two, Fluorocarbon Spraying Technical Requirements and Standards
Fluorocarbon Spraying, as a means of high-grade surface coating process, the quality of the entire process is extremely stringent, in addition to the Fluorocarbon Coatings Manufacturing Plant needs to obtain a quality license to produce the Kynar500-based paint, which is the only one of its kind in the world. In addition to fluorocarbon coating manufacturers need to obtain quality permission to produce Kynar500-based fluorocarbon coatings, the entire surface treatment process with coating manufacturers, including the pre-treatment process, the spraying process to the curing process need to have a strict quality control in order to ensure the quality of aluminum coating. In the fluorocarbon spraying industry today to the American Architectural and Manufacturing Association standard AAMA a 605.02.90 as the main basis for this spraying standard, is recognized as the main international standard to check the quality of the coating international standards. The following are the main indicators of fluorocarbon spraying in the AAMA 605.02.90 standard.
In the AAMA standard, there are many references to South Florida as the test standard because the climate there is known for its humidity, high temperature, and direct sunlight, and is therefore considered to be a hostile environment for coating quality inspection.
There are some other inspection standards in the world similar to the U.S. AAMA-605.02.90 standard, which are also used to judge the quality of fluorocarbon coating. They are:
1. British BS6496-1984 standard "Standard for the coating of architectural aluminum alloy sections and plates".
2. Germany GSBRAL-RC6311994 standard "building aluminum quality inspection standards.
3. Australia AS3715-1989 standard "metal painting standard".
4. South Africa SABS a 1993 "building outdoor aluminum coating standards.
5. Switzerland's "aluminum coating standards for use in the construction industry" 1994.
American Architectural Manufacturers Association standards (extract) AAMA 605.02.90
Three, fluorocarbon spraying equipment and process
Fluorocarbon coating properties of its own decision, spraying equipment must ensure excellent atomization effect. Must ensure that there is excellent atomization effect, to ensure the uniformity of the spray layer, the distribution of metal particles in the fluorocarbon coating, directly affect the appearance of the coating. Uniformity of the coating, excellent quality of fluorocarbon coating has a metallic luster, sharp color and obvious three-dimensional sense. The fluorocarbon coating layer using unsuitable spraying equipment will produce uneven color, shadow on the surface or poor coating. Greatly affecting the decorative effect of fluorocarbon, in order to achieve good spraying effect, are used high-pressure electrostatic electrical spray gun. The United States, Japan, Germany and other countries produce a variety of forms of various brands of spray guns. Each has its own characteristics.
Fluorocarbon spraying process using multi-layer spraying to give full play to the durability of the Kynar500 metal paint, weathering advantages, from the aluminum before the surface treatment to the spraying process requires strict quality control, the final product must meet the U.S. Building Manufacturers Association AAMA-605.02.90 standard.
Fluorocarbon spraying process is:
Pre-treatment process: Degreasing and decontamination of aluminum → washing → alkali washing (degreasing) → washing → pickling → washing → chrome → washing → washing → pure water washing
Spraying process: Spraying of primer → top coat → overcoat varnish → baking (180-250 ℃)→quality inspection
Multi-layer spraying process with three times spraying (referred to as triple spraying), spraying of Bottom surface paint, top coat and overprint paint and secondary spraying (primer, top coat).
1. The purpose of pre-treatment: before spraying aluminum alloy profiles, plates, the surface of the workpiece should be de-oiled and decontaminated and chemical treatment, in order to produce a chrome film, increase the coating and metal surface bonding and oxidation resistance, which is conducive to prolonging the service life of the paint film.
2. Primer coating: as a closed substrate primer coating, its role is to improve the coating resistance to penetration, enhance the protection of the substrate, stabilize the metal surface layer, strengthen the adhesion of the topcoat and the metal surface, you can ensure that the topcoat coating the uniformity of the color, the thickness of the paint layer is generally 5-10 microns.
3. Topcoat: Topcoat is a key layer of the spray layer, which is to provide the decorative color required by the aluminum, so that the appearance of aluminum to meet the design requirements, and to protect the metal surface from the external environment of the atmosphere, acid rain, pollution erosion, to prevent ultraviolet penetration. Greatly enhance the resistance to aging, topcoat coating is sprayed in the thickest layer of paint, paint layer thickness is generally 23-30 microns.
4. Shading paint coating: Shading paint coating is also known as varnish coating, the main purpose is to more effectively enhance the paint layer to resist the erosion of the outside world, to protect the topcoat coating, to increase the metallic luster of the topcoat color, the appearance of a more distinctive color, luster, coating thickness is generally 5-10 microns. The total thickness of the three spray layer is generally 40-60 microns, special needs can be thickened.
5. Curing treatment: three spray layer generally need a second curing, aluminum into the curing oven processing, curing temperature is generally between 180 ℃ -250 ℃, curing time of 15-25 minutes, different fluorocarbon coating manufacturers, will be based on their own coatings, to provide the best temperature and time. Chlorocarbon spraying plant (curium oil plant) also some according to their own experience of the three spraying when the two curing to a curing.
6. Quality inspection: quality inspection should be in accordance with AAMA-605.02.90 standard. Strict quality inspection to ensure high quality spraying products.
Four, the current situation of fluorocarbon spraying in China
With the rapid development of China's construction industry in recent years, the rise of curtain wall industry in China, aluminum profiles require a variety of colors, the rise of the aluminum curtain wall industry, especially in the recognition of aluminum composite panels are not easy to use for high-rise buildings, China's single-layer aluminum panels and aluminum profiles, fluorocarbon spraying layer of the need for an exponential increase over the pre-90s. The original earliest only in Dongguan, Guangdong Province, there are two curium oil plant (i.e., fluorocarbon spraying professional factory) from 95 years to date, China increased to more than 30, also flocked to the handmade and automated, large and small scale, mostly built along the coast. Not only established a professional spraying plant, and there are individual aluminum factory and curtain wall company also invested in building spraying plant, still maintains the enterprise small and full system. Now there are only more than ten officially put into production, there are obvious quality differences.
Domestic new fluorocarbon spraying equipment, mostly for the United States, Germany, Japan design, and the introduction of computer software, the introduction of a variety of countries of different types of electrostatic spray gun. There are hanging type there are semi-suspended, suspended that is, aluminum pre-treatment and spraying, curing process, aluminum is all suspended, by the computer to operate the workpiece in the suspension on the walk. Cleaning, multiple spraying, curing until the spraying is completed out of the product. This fully automated line is not much in the country, and the investment is large. Another for the pretreatment of aluminum plate in several tank liquid processing (such as aluminum anodic oxidation cleaning tank), chroming is also carried out in the tank liquid, and then the aluminum is hung up, the workpiece walks on the hanger, to complete the spraying and curing process until out of the product. Now the domestic hanging line from 100 meters long to the longest 420 meters. General automatic fluorocarbon spraying more for the surface of aluminum spraying, because the length of the aluminum profile is 6 meters, in general automatic hanging six meters long automatic belt suspension and spraying difficulties, early 90 years Hong Kong's earliest in Dongguan, Guangdong Province, the establishment of the first professional curium oil company in Hong Kong called the success of the professional curium oil company, and recently built the nation's longest 420-meter-long automatic hanging fluorocarbon spray line, not only can be sprayed with a variety of specifications, Thickness of aluminum panels, but also can automatically spray six-meter-long aluminum profiles, annual spraying area of 600,000 square meters, but also now the largest and longest, profile plates are automatically sprayed a spraying line.
Any product, manufacturing products, advanced and backward equipment, of course, is an important factor in product quality, but often the equipment is too important, as if as long as the equipment is good, you can produce good products, the fact is not so, the technical software is more important, there is no high level of technical personnel, skilled workers, only good equipment can not produce satisfactory products, as a driver with poor driving skills, driving a Mercedes-Benz sedan, the same will be out of order. Just like a driver with poor driving skills driving a Mercedes-Benz sedan, the same will be an accident. Fluorocarbon spraying technology is extremely strong, in the new domestic spraying line, the formal commissioning of 2-3 months on it, but some commissioning half a year or even longer to adjust the bad, which does not illustrate the importance of technical experience. Recently, there have been projects to cheap, so that a spraying plant has just been commissioned spraying nearly 1,000 square meters of aluminum, the results are: color difference is very large, uneven film thickness, only a small portion can be used, seriously affecting the handover date of the curtain wall, advise the user in the choice of spraying plant, not only to look at the degree of sophistication of the equipment, but also pay attention to the conditions of the technicians and experience, that is, it also attaches great importance to the software, don't just want to be cheap.
In short: fluorocarbon spraying in our country is a relatively new product, we have to understand it to recognize it, in order to use it correctly, I hope that some of the new domestic spraying line, to improve the technology, to sum up the experience, and solid development of fluorocarbon spraying business. There are more than thirty spraying lines in China, and the annual spraying area has exceeded 4 million square meters. Supply exceeds demand, do not repeat the fluorocarbon spraying line for a short time.
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