Since the birth of cars for over a century, car coatings have a history of over 70 years, especially in the past 20 years, which have been rapidly developed. At present, the various functions of car coatings, such as decoration, anti-corrosion, stone impact resistance, workability, and weather resistance, have been greatly improved and have reached a certain level.

With the increasing attention paid to the environment by various countries, the primary development trend of 21st century automobiles is not only to meet the needs of market competition and catch up with the trend, but also to strive to improve the exterior decoration (high gloss, high brightness, multi-color coloring, increased three-dimensional feeling, etc.), friction resistance, stone impact resistance, and resistance to environmental pollution of the coating film. In addition, it is also necessary to reduce environmental pollution during the car painting process.

To control the 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 limited 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 limitation law for car coatings, which limits the VOA emissions of existing coating workshops to the lowest level within 10 years, as shown in Table 5-1. In order to reduce VOC emissions, car paint is being developed towards water-based, high solid, and non isocyanate coatings.

(1) Waterborne Coating

In terms of water-based paint, car original paint is far ahead of car repair paint. As early as the mid-1960s, automotive primers in Europe and North America first completed the process of water-based coating, 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 the market. Among them, the representative company should be Herbests. At present, 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 available for the market. The current successful example of water-based repair paint for sedans 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 technology to largely overcome various inherent defects of previous water-based coatings, and then gives it great market competition potential.

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 advocates the best choice of solvent based high solid component polyurethane or acrylic polyurethane coatings. Aquabase has successfully overcome the inconvenience caused by the strict environmental humidity requirements of the original water-based coatings for construction applications, thus paving the way for entering the car repair paint market.

(2) High Solidification of Coatings

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 were widely used by car manufacturers. The presentation of high solid composition coatings can greatly reduce the volatilization of organic solvents. However, due to various reasons, the slow implementation of high solid composition paint in the car repair industry in China may be related to the lack of strict VOC restrictions in car painting workshops in China so far. As people pay more and more attention to protecting the Earth's environment and reducing atmospheric pollution, they trust that the Chinese government will also formulate practical environmental regulations.

(3) Non isocyanation

Two component polyurethane coatings have many outstanding functions and have been widely welcomed by the coating industry for many years. However, the isocyanate derivatives used here have significant toxicity and are bound to seriously endanger the health of operators. It is understood that countries in the Commonwealth have now 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 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. Organosilicon modified acrylic coatings have the characteristics of super weather resistance, boiling water resistance, resistance to polar media, pollution resistance, as well as smooth, plump, and outstanding mechanical functions of the paint film. By comparing its functionality with traditional acrylic polyurethane coatings, it can be concluded that there is nothing inferior. The only drawback is the high price, and there are still certain difficulties in large-scale implementation. However, with the further development of the silicone industry, the further improvement of technology, and the further decrease of cost, the silicone modified acrylic resin coating will eventually replace traditional polyester polyurethane and acrylic polyurethane coatings, becoming the primary product of the new generation of car repair paint in the 21st century.

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