Research and application of water-based alkyd coating

Coating is an indispensable supporting material for all sectors of the national economy. It is widely used in the decoration and protection of various buildings, various industrial products and vehicles, as well as the anti-corrosion protection of various steel facilities such as docks, offshore oil drilling platforms, power transmission and transformation towers. With the development of science and technology, the functions and application fields of coatings are gradually improving and expanding, and the consumption level of coatings has become an important indicator to measure the economic development level of a country. The problems and development trend of coating industry China is total production of coating has been in the forefront of the world, and has made great progress in the production, variety, quality and technical equipment level of products. However, with the continuous enhancement of people is awareness of environmental protection and the arrival of foreign enterprises after China is accession to the WTO, the existing national coatings industry is facing challenges. How to reduce the pollution caused by the production and use of coatings, especially the air pollution. The pollution of coatings to the atmosphere is mainly caused by volatile organic compounds (VOCs), including hydrocarbons, organic halides, organic sulfides, hydroxyl compounds, organic acids and organic peroxides that can cause changes in atmospheric oxidation capacity and acidity (resulting in acid rain), and may also produce photochemical smog. In the process of coating processing and production, the total amount of VOC released is second only to automobile exhaust, accounting for 20% - 25% of VOC pollution, and mostly occurs in urban and other human populated areas, with very serious pollution. Therefore, reducing and controlling VOC release in coating is a necessary measure to protect the environment. The prevention and control of VOC in western developed countries started earlier.   As early as 1966, the United States formulated and implemented the famous California rule66 law; in 1977, the United States Environmental Protection Agency (EPA) further developed the air purification act ca


(clearairact, CAA), the emission standard of VOC is put forward; in 1990, CAA was further limited and amended. European countries have also set strict VOC emission standards, and the representative is Germany is air purification law. Since the 1980s, China has also formulated some environmental protection laws and regulations. Environmental pressure is affecting the global coating industry, so it is the general trend to develop and promote environmental friendly coatings with low VOC or even zero VOC.   Environmental protection coating refers to water-based coating, high solid coating, powder coating, radiation curing coating, etc. According to statistics, in 1998, the total output of coatings in the United States reached 6.5 million tons, accounting for 25% of the world is total; meanwhile, the market share of environmental protection coatings increased year by year, and the market share of waterborne coatings reached 61.1% in 1999. However, the traditional solvent coating still accounts for 55.5% in China, which is far behind the developed countries. The advantages and disadvantages of water-based coatings can be roughly divided into three types: water soluble, latex and water dispersive. Because water is nontoxic, tasteless, nonflammable and cheap, the introduction of water into coatings can not only reduce the production cost, but also greatly reduce the VOC content, so the development of waterborne coatings is rapid. But just because of the introduction of water, there are a series of new problems. For example, the latent heat of water evaporation is very large, the accelerated drying needs to improve the temperature, and the evaporation speed of water is greatly affected by the relative humidity; the surface tension of water is very large, which has adverse effects on the dispersion of pigment and coating; when the water-based coating is applied to the metal matrix, the high conductivity of water may cause Matrix corrosion, etc. In order to solve the above problems, it is often used to add cosolvent, surfactant, reducing agent and other additives in the coating, and the addition of these additives inevitably brings some negative effects. In a word, the preparation of waterborne coatings is far more complex than solvent based coatings, and there are some shortcomings. However, because it can greatly reduce VOC content, conform to the trend of environmental protection, and meet the performance requirements in many occasions, we have reason to believe that waterborne coatings are a major trend in the development of coatings. The properties and drying mechanism of alkyd resin alkyd resin, epoxy resin, acrylic resin, polyurethane and polyester resin are the main base materials for the preparation of waterborne coatings, among which alkyd resin is a synthetic resin with early development and large output. The development of high-performance waterborne alkyd resin coating is more acceptable to manufacturers for the investment and cycle of product transformation. Another advantage of alkyd resin is that it does not rely on petroleum products. As an important strategic material, the price and supply of petroleum are greatly affected by the international situation. At present, China is oil consumption is largely dependent on imports, so alkyd resin has a unique price advantage. In addition, the components and properties of alkyd resin can be adjusted in a wide range. Only different polyols and polyacids can obtain resins with different properties. The change of the functional ratio between alcohols and acids can control the degree of branching. The number of carbon atoms between carboxyl groups or hydroxyl groups in resin raw materials can adjust the softness of the resin. These characteristics undoubtedly enable alkyd resin to be applied to More areas.