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Since the birth of sedans for a hundred years, car coatings have a history of over 70 years, especially in the past 20 years, which have been rapidly developed. The various functions of car coatings, such as decoration, corrosion resistance, stone impact resistance, workability, and weather resistance, have been greatly improved and improved, reaching a certain level. With the increasing attention paid to the environment by various countries, the main development trend of 21st century automobiles is not only to adapt to the needs of market competition and catch up with trends, but also to strive to improve the exterior decoration (high gloss, high brightness, multi-color coloring, adding three-dimensional sense, etc.), friction resistance, stone impact resistance, and environmental pollution resistance of car coatings. In addition, it is also necessary to reduce environmental pollution during the car coating process. To control environmental pollution caused by production, environmental regulations in the United States and Europe have clear rules for volatile organic compounds (VOCs). German legal rules have restricted VOC emissions since March 1993: 60g/m2 for natural paint coatings and 120g/m2 for metallic flash color coatings. In July 1994, Europe proposed a VOC emission constraint law for car coatings, which limits the existing coating workshops to reduce VOA emissions to the lowest level within 10 years, as shown in Table 5-1. In order to reduce VOC emissions, sedan paint is being developed towards water-based, high solid, and non isocyanate coatings.

(1) In terms of water-based coatings, car original paint is far ahead of car repair paint. As early as the mid-1960s, automotive primers in Europe and North America took the lead in completing the water-based process, and electric ice primers were put into use; In the mid to late 1980s, the water-based primer was also completed; In the early 1990s, water-based gloss varnish also began to enter shopping malls. Among them, the representative company should be Herbests. Now the company has supplied a series of water-based coatings from the bottom to the surface to the car assembly plant. The water-based process of car repair paint is much slower, and so far only a few companies have products to supply to shopping malls. A successful example of water-based repair paint for sedans now is the water-based application of two component polyurethane coatings. ICI company recently launched Aquahase's water-based base paint, which uses advanced micro adhesive synthesis skills to largely overcome the inherent shortcomings of previous water-based coatings, and then gives it great potential for market competition. Aquabase base base paint can be used in conjunction with solvent based two component center coatings or water-based center coatings. As for the glossy topcoat, IC1 company suggests choosing solvent based high solid component polyurethane or acrylic polyurethane based coatings. Aquabase successfully overcame the inconvenience caused by the strict environmental humidity requirements of the original water-based coatings for construction and application, thus paving the way for entering the car repair paint market.

(2) In the 1980s, with the increasing emphasis on environmental protection in various countries, high solid polyurethane high-temperature baking paint, acrylic polyurethane paint, and varnish with high solid composition were widely used by car manufacturers. The emergence of high solid composition coatings can greatly reduce the evaporation of organic solvents. However, due to various reasons, the slow implementation of high solid composition paint in China's car repair industry may be related to the lack of strict VOC constraints in car painting workshops so far. With people's increasing emphasis on protecting the Earth's environment and reducing atmospheric pollution, it is believed that the Chinese government will also formulate practical environmental regulations.

(3) Non isocyanated two component polyurethane coatings have many outstanding functions and have been widely welcomed in the coating industry for many years. However, the isocyanate derivatives used here have significant toxicity and will inevitably seriously endanger the health of operators. It is understood that various countries in the Commonwealth have explicitly prohibited the use of compounds containing isocyanate groups as crosslinking agents in coatings, and countries such as Europe, the United States, and Japan are also preparing to draft relevant laws and regulations to prevent the use of this substance. It is almost certain that after entering the 21st century, the use of derivatives containing isocyanate groups as crosslinking agents for car repair coatings will gradually cease. Recently, Aksu Company in the Netherlands has developed a non isocyanate based two component car repair paint with the product brand AUTOVA. The company introduced that AUTONOVA has almost all the characteristics of a two component polyurethane coating, and the crosslinking agent does not use compounds containing isocyanate groups, which has a particularly fast drying speed and can be dried at low temperatures. The acrylic resin in organic silicon modified acrylic coatings is fundamentally the same as the commonly used acrylic resin in coatings, but it uses alkoxy groups on silane to hydrolyze, condense, and crosslink into a film in the presence of acid, alkali, and organic metal compound catalysts. It is a type of coating that uses non isocyanate derivatives as crosslinking agents. Organic silicon modified acrylic coatings have the characteristics of super weather resistance, boiling water resistance, resistance to polar media, pollution resistance, as well as flat, smooth, full, and good mechanical function of the paint film. By comparing its functionality with traditional acrylic polyurethane coatings, it can be concluded that there are no shortcomings. The only drawback is the high price, and there are still certain difficulties in implementing it on a large scale. However, it is believed that with the further development of the silicone industry, the improvement of skills, and the further reduction of costs, silicone modified acrylic resin coatings will eventually replace traditional polyester polyurethane and acrylic polyurethane coatings and become the main product of the new generation of car repair coatings in the 21st century.

Article source: Qingyuan Automotive Repair Paint http://www.jinliangxincai.com