| Waterborne Coatings is also known as the water-based paints,water dispersion coatings, the water is a major solvent or dispersion medium, resin as the dispersed phase(generally existence as granular), water as the continuous phase. Compared with the traditional solvent paints ,waterborne coatings has the following advantages: (1) Environmental protection: waterborne paints with water as the dispersion medium, contains no organic solvent or only a little. So when we product or construct, there are no more problems of environmental pollution and harmful to human body arising from the organic solvent, also no dangers of explosion and fire during transport and storage; (2) Construction of convenience: Latex paints can be brushing,roller,spraying, also can be diluted with water. Brushing tools can be easily cleaned by water immediately. If them needn't in a short period of time, brushing tools can be immersed in water, or sealed by plastic bags; (3) Coatings drying fast: After painting, with moisture evaporation, coatings dry formation film. In suitable climatic conditions,it dries relatively quickly. The coatings general can be re-painted after about 4h, so we can paint 2-3 times in one day; (4) Good breathability: water-borne coatings is through moisture evaporation, latex particles deformation fuse membrane, so the breathability is good. Good permeability will bring the following benefits: First, compared with the solvent-based coatings, waterborne coatings can be painted on slightly wet grass roots. Second, the temperature is often different inside and outside the room, so there must be moist airflow in the wall.If the film has good breathability, the moisture will be able to go out, and there will be no bubble, shedding phenomenon. Third, it is the good breathability of the coating that greatly eased the dewing problem, and even basically do not dewing. (5) Good water resistance: Water-based paint is one component waterborne coatings, it can be diluted with water for construction.. The film does not dissolve in water, so it has good water resistance. (6) Meet the performance requirements: In its involvement and the use area, regardless of their decorative function, or protection,the waterborne coatings can take on all the responsibilities.This dissertation mainly researched from the following aspects: 1. VOC source research. Because of latex paint with water as the dispersion medium, the VOC is much lower than solvent-based paint ,which primaryly comes from emulsion, solvent , auxiliaries and additives, color and so on, and the most main of them are film auxiliaries and antifreeze such as diol solvent.①Emulsion, the residual monomer in the emulsion is one of the sources of VOC.②Solvent, solvent is a kind of film auxiliaries which is used to improve the film properties. Now the traditional film formation auxiliaries are Texanol, alcohol aether, petrol and benzene methanol etc; Auxiliaries that endow coatings with freeze-thaw stability, such as ethylene glycol, propylene glycol, which are the main sources of VOC.③Auxiliaries and additives, they including certain mineral oil defoamers, association thickening agent to improve the performance of film flowing-flat, and some anti-corrosion bactericide which prevent coatings from deteroprating, auxiliaries and additives for regulating coating system pH, such as AMP-95 etc all contain solvent in different degrees. To control VOC release, we must proceed study from several aspects: Select emulsions which can form film at low temperature without film auxiliaries and solvents ,have good physical and chemical properties and have very low content of residual monomer. Select the low VOC release or no VOC, non-toxic products. Pigment should use good film formation, strong adhesion with substrate, stable composing, low heavy metal content types.2. Influence of each component to waterborne coatings performance research. It detailed analysed the mechanism of each component, respective selected the most suitable types of interior and exterior wall coatings in accordance with the mechanisms, and took into account environmental requirements, selected ingredient of no harm for environment and products of release VOC as little as possible, and filtered the best products combined with the experiment; Then consulted the results of optimization design, selected a series of different dosages to experiment to find one make the paint film performance best, simultaneously, took into account the influence between the various components. In order to endow coatings some special properties to achieve the functional requirements, we also should add some functional additives into the coatings, such as hydrophobic agent, anti-mildew fungicides; It improved the performance of the coating through flexible latex emulsion mixed with ordinary emulsion, added silica sol into emulsion, and other means.3. Explore preparation technics of coatings. According to the physical and chemical properties of some additives, in order to prevent auxiliary agent from volatilization and decomposition in the process of preparation ,the temperature of the process couldn't be too high. So we should control it at least below 50℃. It was best to use recycled water cooling;The requirements of stirring speed at different stages were different. Generally, we mastered four stages: low-speed (400-500 r/min)—high speed (1200-1300 r/min) —middle speed (800-900 r/min)—low-speed (400-500 r/min). We decided the adding order according to the pigment density, water absorption quantity, size decentralization difficulty. We offen follow the principle that the difficult scattered, smaller density, larger water absorption quantity and the smaller size pigment will be added priority.4. Respectively did performance tests for the interior and exterior wall paints we prepared. According to the national standard requirements and targets, we tested the basic performance such as the viscosity, fineness and stability, and other necessary performance such as resistance scrub away, hardness, alkali resistance of the interior walls,the testing results all met the requirements, some of them and the release of toxic substance even far overstepped the national standard scope; In addition to above basic performance, we also increased some special performance which were fit for the external wall requirements such as water resistance, temperature change resistance,aging resistance, stain resistance.The test results were outstanding.
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