All water as a solvent or as a dispersion medium coating, can be called water-based coating. Water-based coatings include water-soluble coatings, water-diluted coatings, water-dispersive coatings (latex coatings) 3 kinds. Water-soluble coatings are water-soluble resins as film forming materials, represented by polyvinyl alcohol and its various modifiers, in addition to water-soluble alkyd resins, water-soluble epoxy resins and inorganic macromolecular water-based resins.
Second, the advantages and disadvantages of waterborne coatings
Water-based coating is a relatively new coating on the current coating market, many people do not have a correct understanding of water-based coating, water-based coating relative to solvent paint coating, has the following characteristics:
Advantages of water-based coating:
1. Paint tells you that waterborne paint to water as a solvent, save a lot of resources; Water-based paint eliminates the risk of fire during construction. Reduced air pollution; Water - based coatings only use a small amount of low toxic alcohol ether organic solvents to improve the operating environment.
Generally, the organic solvent of water-based coating (accounting for coating) is between 10% and 15%, while the current cathodic electrophoretic coating has been reduced to less than 1.2%, which has a significant effect on reducing pollution and saving resources.
2. Water-based coating can be directly applied to wet surface and wet environment; Water - based coatings have good surface adaptability and strong adhesion.
3. Water-based coating tools can be cleaned with water, greatly reducing the consumption of cleaning solvent.
4. Water-based paint electrophoretic coating film is uniform and flat. Good flatness; The inner cavity, welding seam, edges and edges can be coated with a certain thickness of film, with good protection; The electrophoretic coating has the best corrosion resistance, and the salt spray resistance of thick film cathodic electrophoretic coating can reach up to 1200h.
Problems existing in waterborne coatings
1. Water-based coatings have high requirements on the surface cleanliness of the construction process and materials. Due to the high surface tension of water, dirt can easily cause shrinkage cavity in the coating;
2. Poor dispersion stability of water-based coatings against strong mechanical forces, when the velocity in the pipeline changes rapidly, dispersed particles are compressed into solid particles, resulting in film pitting. Good shape of conveying pipe and no defect of pipe wall are required.
3. Paint tells us that waterborne paint is corrosive to coating equipment, corrosion resistant lining or stainless steel material should be used, equipment cost is high. Water - based coating on the corrosion of the pipeline, metal dissolution, so that dispersed particles precipitation, film produced pitting, also need to use stainless steel tube.
4. Baking water-based coatings have strict requirements on the construction environment conditions (temperature and humidity), increasing the investment of temperature and humidity control equipment, and increasing energy consumption.
5. Water based coating water evaporation latent heat, baking energy consumption. Cathodic electrophoretic coating should be baked at 180℃. Latex paint, on the other hand, takes a long time to dry completely.
6. Water-based coatings with high boiling point of organic solvents, such as when baking produce a lot of soot, condensation drops on the surface of the film to affect the appearance.
7 waterborne coatings have poor water resistance, so that the coating and bath stability is poor, poor water resistance film. The medium of water-based coating is generally slightly alkaline (pH7.5 ~ pH8.5), the ester bond in the resin is easy to hydrolyze and make the molecular chain degradation, affect the coating and bath stability, and coating film performance. Although there are many problems in waterborne coatings, but through the formula and coating process and equipment and other aspects of technology to improve, some problems in the process to be prevented, some through the formula itself to improve and improve.
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