Because traditional coatings have an impact on the environment and human health, people are now trying to develop green coatings. The so-called "green coatings" refer to energy-saving, low-polluting water-based coatings, powder coatings, and high-solid content coatings (or solvent-free coatings). ) and radiation curing coatings, etc. Before the 1970s, almost all coatings were solvent-based. Since the 1970s, due to the high price of solvents and the increasingly stringent requirements for reducing VOC emissions, more and more coatings with low organic solvent content and no organic solvent have been greatly developed. More and more green paints are used now. The following new paints are the best developed paints.
①Solvent-based coatings with solid content. High-solid content solvent-based coatings are developed on the basis of common solvent-based coatings in order to meet increasingly stringent environmental protection requirements. Its main feature is that on the premise that the original production method and coating process can be used, the amount of organic solvent is reduced, thereby increasing the solid content. Such coatings have been developed centered on the United States since the early 1980s. Typical low solids solventborne coatings are 30% to 50% solids, while high solids solventborne (HSSC) require 65% to 85% solids to meet increasingly stringent VOC restrictions. In the formulation process, the use of some non-VOC solvents as diluents is a workaround for strict VOC restrictions, such as acetone. A very small amount of acetone can significantly reduce the viscosity, but because acetone volatilizes too quickly, it can cause a potential fire and explosion hazard and needs to be strictly controlled.
②Water-based paint. Water is different from most organic solvents in that it is non-toxic, odorless and non-flammable. The introduction of water into coatings can not only reduce the cost of coatings and the fire caused by the presence of organic solvents during construction, but also greatly reduce VOCs. . Therefore, water-based coatings have made great progress and development since their appearance. China Environmental Labeling Certification Committee promulgated the "Technical Requirements for Water-based Paint Environmental Labeling Products", which stipulates that the volatile organic compound content in the product should be less than 250g/L; Less than 500mg/kg (calculated as lead); formaldehyde and polymers shall not be artificially added during the production process, and the content should be less than 500mg/kg. In fact, water-based paints now account for about half of all paints. There are three main types of water-based coatings: water-soluble, water-dispersible and latex.
③ Dust coating. Dust coating is a relatively advanced coating in China. In theory, dust coatings are absolutely zero-VOC coatings, which have their own unique advantages. Perhaps after VOC is completely abandoned in the future, dust coatings will be one of the most important directions for the development of coatings. However, the limitations of its application require more extensive and in-depth research. For example, its manufacturing process is relatively complicated, the cost of coating manufacturing is high, and the baking temperature of dust coatings is much higher than that of general coatings, making it difficult to obtain thin coatings. The paint color is poor, and the uniform coating of irregular objects is poor. These all need further improvement, but it is one of the future directions.
④ Liquid solvent-free paint. Liquid solvent-free coatings that do not contain organic solvents include two-component, energy beam curing, and the like. The latest development trend of liquid solvent-free coatings is the development of single-component liquid solvent-free coatings that can be constructed by ordinary brushing and spraying.
The research and development direction of coatings is becoming more and more clear, that is, to seek coatings with VOCs that are continuously reduced to zero, and whose application range should be as wide as possible, superior performance, and appropriate equipment investment. Therefore, water-based coatings, powder coatings, solvent-free coatings, etc. may become the main direction of future coatings development.
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