The human body will also cause damage to the circulatory system, central nervous system, liver, lungs, etc. after inhaling a certain amount of organic solvents. These organic substances enter the atmosphere and react with nitrogen oxides, producing photochemical smog harmful to humans, seriously polluting the atmosphere, affecting biological growth and human health; in addition, the death of forests is also related to the pollution of the atmosphere by organic solvents. At present, the developed countries in the world have legal regulations on the volatile organic matter (VOC) of coatings. For example, the VOC value in Europe must be lower than 459/n1, and the v0C value in Germany must be lower than 409/n12.
Under such strict regulations, automotive coating experts must either adopt new VC coatings; or modify equipment to recover solvents. However, solvent recovery equipment costs a lot of money and it is difficult to use recovered solvents, so the use of new paints becomes the only way out. In fact, automotive coatings are developing in the direction of water-based electrophoretic primers, water-based intermediate coatings, and topcoats. Below, the author makes some discussion on the performance comparison of water-based coatings and other coatings.
Performance comparison of water-based coatings and other coatings. Environmentally friendly coatings represented by low-solvent and solvent-free coatings mainly include the following types: 1. Water-soluble coatings 2. Water-dispersed coatings are called paints and coatings 3. Low-solvent and high-solid coatings 4. .Powder coatings 5. Radiation curable coatings. The research and development of water-based coatings in China began in the 1960s. Due to the compatibility and protection of this coating to the environment, the country vigorously supported the development of water-based coatings after entering the 90s. Water-based coatings and market share are rapidly increasing. Paints that use water as a solvent or dispersion medium are called water-based (sexual) paints.
After the 1990s, water-based coatings have formed a multi-functional, multi-purpose and huge coating system, becoming one of the most promising environmental protection coatings in the 21st century. The annual growth rate of industrial water-based coatings is 6% to 8%, and they account for 5% of the total coatings (including electrodeposition coatings), while emulsion coatings (including resin-bonded mortars) account for 40%, which is a particularly fast-growing industrial dispersion Coatings only account for 2% 3% of the coatings market. Water-soluble and emulsion coatings are on par with traditional solvent coatings in terms of their viscosity and other important properties.
The amount of organic matter released by various coating systems The amount of organic matter released by the coating system (expressed as its percentage of solids) Traditional liquid coatings (solid content 50%) 100% medium solid content liquid coatings (solid content 60%) 67% class Solid content liquid coatings (solid content 70%) 43% Class II solid content liquid coatings (solid content 80%) 25% water-soluble resin coatings 5% 25% water-based dispersion coatings 3% organic matter release of various coating systems see 2. For water-based paints, the release of organic solvents is scored as: E=dpw off/wE unit area paint film organic solution agent release; unit g/In2, p paint film density; unit g/ln2w well paint organic Solvent content; w paint mass fraction; d paint film thickness. The general solid content of water-based paints is about 50% when put into use, and the water-based paints containing 2% and 12% of organic solvents have the same solid content as 75% in terms of solvent release. %90% solvent paint (low solvent and high solids paint) is equivalent.
The amount of organic solvent released by the water-based coatings currently used is lower than that of most solvent coatings, because the solid content of solvent coatings exceeds 70%. According to reports, in 1991, German automobile production was 500,000, and paint consumption was 100,000 tons. 50,000 tons of volatile organic solvents are emitted, and the data of the European automotive coating industry is more than double that, that is, 100,000 tons of toxic solvents are emitted into the atmosphere every year.
Obviously, solvent coatings consume the most energy, while water-based coatings are equivalent to high solids coatings. In addition, the safety performance is good, and the use of water-based paint has the highest safety factor. Since the solvent of water-based coatings is water instead of flammable solvents, there is no danger of combustion and explosion during the construction process. For solvent-based coatings, due to the presence of organic solvents, it is quite dangerous when drying and heating. Moreover, in order to overcome the explosion hazard, the air circulation speed (amount) of the solvent coating during heating (baking) must be particularly large to take away the volatile solvent and keep it below the explosion limit. In this way, water-based paint can save a lot of energy.
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