Development direction of coating technology

Coating material, coating process, coating equipment and coating management are four major elements of automobile painting, which complement each other, and promote the progress and development of coating process and technology. Twenty-first Century is called the new century facing environment, environmental protection has attracted worldwide attention, and has become the most urgent subject of human research. The painting of automobile and its parts is one of the links with the highest energy consumption and the most waste generated in the process of automobile manufacturing. Therefore, reducing coating pollution, reducing coating cost and improving coating quality have been the theme of coating technology development.

Application of new coating materials

The application of new coating materials is the forerunner of coating technology progress. Under the premise of meeting the performance requirements of coatings, the main target of development is to reduce the pollution and reduce the coating cost.

Prepared from biodegradable surfactant degreasing agent, nickel free phosphating solution, nitrite phosphating and non chromium passivation agent, low temperature degreasing agent (processing temperature of 43 DEG C), the same performance with conventional low temperature (35 DEG C) Shao Zha (10% ~ 30% lower than that of conventional phosphating solution, Wuxi) lead-free cathodic electrophoretic coating and low temperature curing (160 degrees 10min), low heating loss (less than 4%), low VOC volatilization (0.4% ~ 0.8%) type cathodic electrophoretic coatings have been applied for many years in Europe and japan. In North America and Europe, alternative two coat electrophoretic coatings have been applied.

In Europe, some automobile companies have applied waterborne coatings on the new coating line in recent years, and VOC emissions have been lower than the required 35g/m2 (Germany TA-Luft, 1995). Since 1990s, all new painting line primers have been used with electrophoretic primer or powder coating. The coating is made of water-based paint or high solid material, and the topcoat is made of water-based primer. At present, powder varnish has been applied to car body painting. After the industrial application of powder coating varnish, the powder metal base has been commercialized. In North America, powder coating has been industrialized for many years. At the same time, waterborne topcoat has been popularized very quickly in recent years, and high solid medium coating and finish coat are also very popular. The application of UV curable (UV) coatings in automotive coatings is nearing maturity. Japan is also actively developing and promoting waterborne coatings, high solids and ultra high solid coatings.

With the deterioration of the global environment, we must greatly improve the acid rain resistance and scratch resistance of automotive coatings. In recent years, decreasing the body inside and outside surface of the bottom film thickness difference electrophoresis high throwpower electrophoretic coating, acid rain, low pigment and anti abrasion coating, the coating and the multicolor paint viscosity control technology has been widely used. Several major automobile companies in China application processing materials and electrophoretic paint in the paint before with the international level difference is not big, but due to the application of waterborne coating and water-based paint must use special equipment, thus increasing the cost of painting. Although foreign owned and joint ventures with domestic production capacity in water in the coating and water-based paint, but in automobile coating coating and topcoat is still using the traditional low solid solvent coatings, coating VOC emissions far behind europe.

Coating process and equipment

In recent more than 10 years, the progress of coating process and equipment is mainly reflected in the application of environmental protection coating materials, reducing the waste water and waste residue emissions, reducing costs, optimizing the automobile production process and so on. Due to the progress of coating materials, the design of automotive body coating system has also made revolutionary progress. Several typical new coating systems and new technologies have been or will be used in industrial production. At present, the coating process and equipment in our country are equivalent to the level of 10 years ago in Europe and America. Some enterprises have adopted some advanced equipment in the new painting line.

1. water saving and waste recycling technology

Pretreatment and electrophoresis are the most important links of water consumption and wastewater discharge in automobile painting. With the continuous development of membrane technology, membrane separation technology (UF and RO) is used to recover the degreasing fluid, to regenerate washing water and pretreatment wastewater, so that it is possible to realize the real meaning of electrophoresis closed circuit cleaning. At present, membrane separation technology has begun to be applied.

In recent years, with the industrialization of developed countries environmental protection coating, recycling technology of some coatings (such as powder slurry recycling technology, powder color and varnish recycling technology, waste paint flocculation ultrafiltration, dryer technology, cooling method and electrostatic adsorption recovery water paint technology, painting fog water paint recycling etc) can also be applied, so as to make the painting line to further improve the utilization efficiency of coatings, minimizing waste paint slag discharge.

At present, our country pays little attention to the water saving and comprehensive utilization of the three wastes, and is relatively backward in the application of new technology.

2. kinds of new car body painting process

Reverse process: the powder coating is sprayed on the outer surface of the car body, and then the coating is sprayed after hot melting, and then the powder / electrophoresis coating is dried together. The use of this technology can reduce the amount of 60% of the electrophoretic coating, powder coating electrodeposition primer is 70 m with the thickness of the outer surface of the body and replace the coating, coating and drying process so as to save materials and cancel, energy costs, reduce emissions of VOC.

Two electrophoresis process: two coating electrophoresis material was used, and second layer electrophoresis (35~40 m) was used instead of medium coating. The automatic construction of electrophoresis process has high stability, high reliability, high qualified rate, high material utilization rate and less equipment investment (no air conditioning system), so it can save 48% of the cost and reduce the maintenance frequency